If you own Snake Eater, trade it in for Subsistence, YOU WONT BE DISAPPOINTED!
This brings me to Subsistence. First off, there's two discs. Disc 2 has things like a new Snake vs Monkey mode, Two duel modes to fight against your favorite boss(es), about 15-20 bloopers that they made from oringial cut scenes from the game that are all funny in their own way, but best of all an online mode which I am looking forward to playing this summer when I don't have a firewall blocking my ps2 connection. PLUS, you get the first two metal gear games as well. So, disc 2 alone will give you quite a few hours of play time, not even including the online mode.
The game is of course on disc one. Something I noticed after starting a game and then saving, on the main menu you will get what's called demo theater, which is like watching the cut scenes concurrently which is highly similar to the special edition's 3rd disc three hour movie (didn't get my hands on a special edition :( ). But to cut the crap and get to the game, you will notice things being added right off the bat. One thing is you have more camo to choose from and this time they do special abilities. For example, brown face paint gives you infinite O2 so you can be underwater all you want. The body camo will give you an ability such as 2/3 damage reducal, no reduction of supressor life, or no reduction of battery life. Also, the new camera is awesome! It takes the limited Metal Gear 3 world and makes it completely 3 dimensional, only adding even more shine onto the beautiful world created for this game.
Of course at the end you can unlock a ton of crazy stuff to play in the next time through, and even somethings have been switched around like where some guards patrol. But, for $30 this is the best bargain you will find at any store. Metal Gear Solid 3 Subsistence is THE BEST game out for the PS2. Nothing pushes the graphics like this game, and nothing has as close a replay value (except FFX perhaps, but after 100 hours or so that game gets so old you never wanna touch it again, besides, shooting people is so much more fun!). Metal Gear Solid is more than a game, it's one of a kind!
P.S., please note on my 100 hours or more that this includes play time of Snake Eater, I figure since the controls and everything are about the same it counts towards that.