A classic game with a million remakes, the question is just which one you want.
Sound and graphics are your old circle circles and beeps. Nothing special by any means, but it gets the job done. You can't pretty up Pac-Man very much which is why it never seems to get much of a make over. Right here though is definitely the old school version in every way.
Gameplay translated just fine to the Wii. There's no slowdown or unresponsive type issues. It would be really cool if there were some sort of joystick you could use to play the game to really give it that old school arcade feel, but using the sideways Wii-mote gets the job done.
There's really no question of what your getting into with this purchase and for most people it's probably not worth the five bucks. Personally, I bought it for the convenience of having it on my Wii everywhere I go and I happen to have 500 points burning a hole in my pocket at the time. Those others of you that buy it will probably be in a similar situation unless your just hardcore Pac-Man enthusiasts.
I can honestly say though I don't regret it and I have fun playing a game or two when I wake up in the morning before getting on with my day. So, if you're in a situation like I was at the time I'd say go for it, but if not just pass it up and play one of your other versions I'm sure you already own.