I wont mind getting Pac Man but I haev yet to take my 360 online.
You gotta get online! In addition to Xbox Live Arcade for classic titles, there's a swarm of original xbox arcade games out there to try out that have that classic arcade "feel" to them, and in some cases are actually better than the old staples.
There's also tons of free demos to try out (for both the arcade and new releases), game videos (new halo 3 and Mass Effect are out), movie trailers, not to mention dowloadable content, etc.
And you can just use your existing xbox live account (that is, if you have one) to access all of it.
Personally, I've been very impressed with it.
Just my $.02.