Well, what else can I say. It's Pac Man.
There are certain factors in this port that alter the gameplay of the original to an extent. Instead of seeing the entire maze at once, you can only see the part of the maze that Pac Man is currently in, meaning that you won't always know where the ghosts are. Also, the lack of color makes all the ghosts look the same, meaning you won't know which ghost is chasing you. These elements up the challenge a bit, but it's still pretty much the game you remember.
There is also an interesting 2-player mode in which two players race to complete four levels. When you eat a ghost, it gets transferred to the other GameBoy, meaning your opponent will have even more ghosts to worry about. However, if you don't have a linker cable and a friend who also owns this game, then you won't be able to experience this mode.
On it's own merits, Pac Man is a fun game. However, with it's lack of much bonus content, this version is just not worth paying even the bargain price you can get it at nowadays. If you really want to play Pac Man whenever you want, I'd reccomend getting a Namco Museum game. Also, Pac Man World, as well as it's sequel, have the original Pac Man as a bonus feature. And if you must play Pac Man wherever you want, then I'd reccomend getting either Pac Man Collection or a portable Namco Museum game.