Pros: -the cartridges have NO repeats.
-comes with free controller
-can play 2-PLAYER games
-9V adapter compatible
-has AUTOFIRE A & B buttons
-four button Dpad, PS style
-more comfortable to hold
-looks exactly like a...(you know what)

Cons: -speaker is on the back
-player 2 port is 9-pin (nes is 7pin)
-quality.. well, pretty much what you'd expect.

Other Thoughts: don't make the mistake of comparing this with other handhelds. in some aspects this is vastly superior to the onestation, first of all it has a 9V power port, so you can plug in the adapter while playing if your batteries get low. BTW, switching from batteries to Adapter wont affect your game. and it uses 4 AAA batteries instead of 3 AAA, for longer play time. the included cartridge has some really good games on it, with almost NO REPEATS. yes, it really does have over 100 games. you can even use it without the cartridge as there are 5 games built in.
and, unlike the onestation, it has AUTOFIRE A and B buttons. and most importantly, THE BUTTONS ARE ACTUALLY CONFIGURED THE PROPER WAY! yes, left button is "B", right button is "A". a MUST for games like super mario or lode runner. definitely more ergonomically designed than other handhelds that have the buttons mixed up.
oh yeah, that port on the bottom, its for playing 2 PLAYER GAMES. also, you could plug in a light gun for DUCK HUNT.

Bottomline: now the bad, the speaker is located on the back, so you cant really hear the sound very well, but it does have a headphone jack. also, the controller port is 9-pin famiclone style, the standard of most pirate NES systems. and you cant buy just 9-pin controllers anywhere. the overall quality of this isn't great, but then again what did you expect.