Update:
I just recently got the brand new Gameshark v. 2.0, and I am happy to say that Interact has finally made a much more reliable Gameshark. It freezes half as much as earlier versions, and works much smoother. I thought 1.9 was pretty good, but I guess it was just temporary until Interact could get out this one. Trust me, get this product, you won't be disappointed. Versions 1.9 and below still gets a 7.3, but if you get 2.0, take that score and bump it up to a solid 8.0.

Versions 1.9 and Below Review:
It's really hard to review this product, seeing as there are so many versions. The latest, ver. 1.9, is a million times better than its predecessors thankfully. Unlike the other versions on such systems as Nintendo 64 and the original Playstation, it does not just simply plug in to the console. It is a small card that goes into the memory card slot. Along with it is a disc that has to inserted first. With this, you have to search for the code you wish to use, select it, the press "play game with cheats." After this, you have to open the disc tray, and put in the game you want. While this is much more of a hassle than previous kinds, it still works rather well.

Gameshark is a savior for some gamers, but also a sign of disrespect for others. Many believe that a game should be beat on its own, otherwise it will not be fun. This is simply not true. I believe that the first time through a game, cheats shouldn't be used. After that, all bets are off. Gameshark allows such game codes like infinite ammo, infinite items, and the best, infinite life. For gamers who have played through a huge game like Metal Gear Solid 2, they usually don't want to play the whole thing again. Gameshark makes it so you don't have to. Now you can have infinite ammo, and just go psycho on the enemies.

Interact is known for usually making pretty good products, and this is no exception. There are several flaws though. The first and most obvious is the fact that it freezes the game often. In the middle of a game, it will just turn off. This happens way more than it should, but Interact has said that they are "working on it." Another flaw is that some games do not allow a player to save to a memory card that is in slot 2. Since this is where the Gameshark card goes, saving is not always possible. Lastly, there are many bugs. Sometimes a disc won't read, a code disappears, or the whole thing stops working all together.

All in all, Gameshark is a great thing for gamers who believe there is nothing left to accomplish. If you are expecting a great working, never-failing cheat device, look elsewhere.