American Pie
Basic Instinct
Cinema Paradiso
Charlie's Angels
Clerks
Crouching Tiger, Hidden Dragon
Die Hard
Hero
Lord of the Rings Trilogy (does it count if one is the theatrical, the other the extended edition?)
Pulp Fiction
Shakespeare in Love
There's Something About Mary
Trainspotting


Would LOVE to double-dip (for an anamorphic upgrade): The American President, Annie Hall, Elizabeth, Emma, Four Weddings and a Funeral, The Graduate, He Got Game, Sliding Doors

Se7en
ScarFace
GoodFella's
Pulp Fiction
Res.Dogs

Se7en
Pulp Fiction

LOTR:FOTR (sort of, theatrical was an unexpected gift, else I'd have rented and waited for EE like I did with TTT and ROTK).

I have double dipped for:
The Good, The Bad and the Ugly
Silence of the Lambs
Trainspotting
Clerks
Dr Strangelove
Re-Animator
Night of the Living Dead
Bourne Identity
English Patient
Reservoir Dogs
Léon
M

I also have two copies of Mallrats cause I clearly have some mental problems

I have Triple dipped:
2001: a spce odyssey - One of my alltime favourites so I am trying to get all versions
Evil Dead - For some reason I can't help buying those old Anchor Bay super jewel versions with the 5 variant covers.

Frankenstein, Bride of Frankenstein, Creature from the Black Lagoon
Strangers on a Train

Malcolm X
The Shawshank Redemption
The Matrix Trilogy
Animatrix
Matrix Revisited
Planet of the Apes (1968)
Star Trek: The Original Series
Star Trek II: The Wrath of Khan
Star Trek III: The Search for Spock
Star Trek VI: The Undiscovered Country
Terminator 2
X-Men
2001: A Space Odyssey

Stargate
Fellowship of the Ring (LOTR)
Eternal Sunshine of the Spotless Mind
Clerks
Dawn of the Dead (Original)
X-Men

Dawn of The Dead(1978)
Day of the Dead
Friday The 13th(have uncut Region 4)
Zombi
About to double dip on Aliens

Double Dip selling off the surpassed edition;
Aliens
LOTR FOTR
LOTR TTT
LOTR ROTK
Singles R1 changed to R4 just for the Amray case
Princess Bride
Matrix Reloaded
Matrix Revolutions
Babylon 5 In the Beginning/The Gathering
Batman (sold off 4 pack in disgust, then reconsidered and re-bought this)
Batman Returns (ditto)
Battle of Britain (R1) for R4 DTS 2 disk
A Bridge Too Far (R1) for R4 2 disc
Casablanca
Dead Poets Society
StarMan (R1) for R2 (commentary)
Demolition Man (R4) for R1 (undubbed Taco-Bell/Pizza Hutt, and commentary)
Empire Records for Fan remix edition (though I think the sound might be better on the original)
Fried Green Tomatoes (R4) FS for R1 WS S/E
Leon The Professional
Monty Python and the Holy Grail (R4) FS for R1 S/E
The Replacement Killers R4 std for R1 S/E
Saving Private Ryan for DTS 2 disk
Starship troopers R4 (1x com) for R1 (2x commentaries)



Double dip keeping both disks;
Bad Taste (Anchor Bay 2 disk) and R4 (for the commentary)
Matrix
Star Wars 1997 Episode 4 (worthless now)
Star Wars 1997 Episode 5 (worthless now)
Star Wars 1997 Episode 5 (worthless now)
Terminator 2 U/E for DTS and E/E for Com

Quadruple dip keeping the last 2;
Fifth Element (R4) for Superbit, then (R1) Ultimate and R2 S/E (for commentary)

Quadruple Dip.... blood hell this has got out of control!!!

I did quite a bit of double-dipping a few months ago, during Blockbuster’s brief $8 trade-in offer. Since I picked up most (not all) of the new editions as Columbia House enrollments* or during B&M sales** ($5-10 each), I pretty much broke even (or made a few dollars, in some cases):

The 400 Blows (upgraded to Criterion)
8 1/2 (upgraded to Criterion)
Alien*
Aliens*
All About Eve**
Black Hawk Down*
Brazil (upgraded to Criterion)
Buck Privates
Buck Privates Come Home
Casablanca*
Cinema Paradiso*
Clerks**
Do the Right Thing (upgraded to Criterion)
Escape from New York*
Fargo**
Groundhog Day**
Gone with the Wind
The Good, the Bad and the Ugly*
Goodfellas (upgrade in box set)
The Great Escape*
The Happy Gilmore/Billy Madison Collection (Widescreen)**
The Hunt for Red October**
(Abbott & Costello) In the Navy
Jerry Maguire*
A League of Their Own*
M (upgraded Criterion to new Criterion edition)
The Manchurian Candidate (1962)**
Mary Poppins
Mulan
My Fair Lady**
My Man Godfrey (upgraded to Criterion)
The Nutty Professor (1963)**
One Flew Over the Cuckoo’s Nest*
The Pink Panther Collection**
The Princess Bride**
The Philadelphia Story (upgrade in box set)
Patriot Games**
Pulp Fiction*
Raging Bull (upgrade in box set)
Showgirls**
Sixteen Candles**
South Park
Terminator 2: Judgment Day
Thelma and Louise**
There's Something About Mary*
Unforgiven*

Queen Margot.....R2, R4.

Ciao,
Pro-B

Alien
Aliens
Alien 3
Alien Resurrection
Hellboy
T2
Lord of the Rings Trilogy
Matrix Trilogy
Robocop

I've double-dipped many many times, but as far as I can remember, only one triple-dip so far:
Amityville II The Possession
(Italian release, old UK release and now the R1 release)

Saving Private Ryan - had the original DD version, got the DTS version, then sold both to get the World War II Collection when Costco had it cheap.

A Bug's Life - Upgraded to the new Collector's Edition when Costco had it cheap.

From Russia With Love (I think, some James Bond one) - Had an individual copy, then found a used set and sold the one in the set.

Almost Famous
Billy Madison
Clerks
Daredevil
Dogma
Freaks & Geeks
The Good the Bad and the Ugly
Happy Gilmore
The Lord of the Rings: The Fellowship of the Ring
The Lord of the Rings: The Two Towers
The Lord of the Rings: The Return of the King
Memento
Predator
Scarface (boxset and anniversary)
Top Gun
X-Men

I don't double dip; I upgrade.

I'm unsure as to how many I've upgraded.

Nothing that I can recall. I don't play that game and have been lucky up to this point. I'd rather spend my money on something I don't already have. I'm not saying it will never happen, but it hasn't yet (~400 titles).

Unless you count movies that have been replaced because of box sets (for example, I already had Psycho and got another copy when I bought the big Hitchcock box set). I wouldn't call that a double dip personally.

Triple:
A Clockwork Orange (Mono Region 1, DD5.1 Region 2, Deluxe Region 2)

Double:
Dawn of the Dead (AB Theatrical, AB Ultimate Edition)
Star Wars: Attack of the Clones (Star Wars Saga/Stand Alone)

Thankfully just Terminator 2

Heat
Get Shorty
Matrix Reloaded
Resovoir Dogs
Something about Mary

Soon
Clerks
Mallrats
SpaceBalls
Rounders
Held Out For
Goodfellas
Pulp Fiction
True Romance
Aliens
Bridget Jones
Matrix (Ultimate)
Meet the Parents
Platoon
Princess Bride
Shawshank Redemption
Swingers

Caved in and double-dipped on Ghostbusters since the new box set was so cheap. Getting the new Batman box set, so there's even more double-dipping.

Boogie Nights
Carlito's Way
Reservior Dogs
Dazed & Confused
Donnie Darko

Fight Club (so I wouldn't have to open my oop 2 disc set...damn re-releases)
Lawrence of Arabia (before I know what a Superbit was)
The Good, The Bad, The Ugly (resale on old version not worth the hassle)
LOTR: FOTR (couldn't wait)
LOTR: ROTK (couldn't wait)

And some likely double dips in the future:
The Lost Boys
The Fog
The Thing

Add Silence of the Lambs and Gladiator to that.

Hrmm.. not counting titles that are different cuts of the movie (ie Lord of the Rings theatrical vs. extended, Apocalypse Now vs. Apocalypse Now Redux)

Silence of the Lambs (later got rid of the MGM edition, preferred the Criterion)
This is Spinal Tap (kept both CC & MGM)
Swingers
Clerks
Mallrats
The Trouble with Harry
Psycho
Vertigo
Rear Window
The Good the Bad and the Ugly
The Great Escape
The Man Who Fell to Earth
Traffic
Chungking Express (individual --> box set)
Days of Being Wild (asian import --> Kino version)
Transformers: Heroes
Transformers: Villains
Metropolis (triple --> madacy --> Kino --> Fritz Lang set)
M
Smokey & The Bandit (standard --> pursuit pack)
Goodfellas
Bullitt
The Getaway
Papillon
Kubrick Collection (original set --> restored/remastered edition)
Spartacus (universal --> Criterion)
Longest Yard (original --> lockdown edition)


Wow, more than I thought... "Ran" and "Wages of Fear" will be added to this list shortly...