Faithful and enjoyable port of the arcade classic, but most achievements are so easy, it feels like cheating.
That said, should you buy it for what is most likely the fifth time? I myself own four or five copies of Pac-Man in some form or another, be it mobile phone, unlockable in other Namco games or simply Namco Museum. The answer really boils down to three points.
First, the achievements are--like Galaga--incredibly easy to obtain, thanks to a completely unnecessary level selection feature that allows you to pick up where you left off. While arcade noobs may appreciate this feature, as well as those out looking for a quick 200 points--obtainable within an hour--the honest and/or hardcore will want to look elsewhere for their challenging achievement fix. The hardest of these is chowing down four sets of ghosts in a single stage (four per power pellet).
When I get an achievement in Robotron: 2084, I am proud to have improved to the point where I can show the world that I suck less. When I blow through 10 out of 12 achievements in Pac-Man within an hour of it's release onto Marketplace, I feel guilty, as if somehow I have cheated. Granted, while nobody is putting a gun to your head, forcing you to use the level selection feature, most of us will.
Second question: Do you like competing with your friends to see who has the higher score? Leaderboards are here and will allow you to boast with speed and precision.
Thirdly is the multiple purchase factor. Do you care about achievements or simply consider them a bonus, secondary to the enjoyment of classic Pac-Man action? Do you care about Leaderboards on which you may compete with your friends for bragging rights? Do you even have any friends? Then look at how many copies of the original, arcade Pac-Man you own. If the number is greater than zero, save your 400 points for something else.