Tycho at Penny Arcade planted the seed last week when he wrote:
“If Pac-Man CE remains on Live Arcade only it will be a criminal act, and I will work to bring these evil men to justice. I downloaded the demo expecting disposable content, consistent with the necrophilia on display elsewhere in the classic coin-op section. After one round, this demo I grabbed explicitly to revile had become a sale, and a week later it is an obsession and perhaps even a lifestyle…It’s absolutely critical that you grab the demo, at the very least. You’ll be surprised by its vitality and relevance.”
I know he’s given to hyperbole so I swallowed that grain of salt. Plus, I rarely download any demos. 80% of my video game time is spent playing Gears of War with the guys, and the other 20% is split between Tiger Woods and Guitar Hero II. My game time is at a premium, so while I was waiting to get a GoW game together on Friday I, with an assist to the nice people at Anheuser Busch, downloaded the Pac Man C.E. demo.

It was so damn good I bought it and it was all I played this weekend. BIG FUN. There are a lot of elements that are unique to the C.E. version (you can see them listed here) but the main ideas: run, eat, run more; are all classic PacMan.
If you ever enjoyed any of the Pac Family of games you should definitely check out this demo.