I'm looking into the same thing. I have an older (3.5 years) PC as my home computer, attached to my HDTV, and it's probably unnecessary (and certainly not as good a fit) with my MBP, iPad, iPhone, etc.
I'm trying to decide between a mac mini, which will give me full computer functionality, or Apple TV, which will give me 90% of what I need. I won't have a CD/DVD option, bluray will not be available (not that it would be with a mini), and I'll need to leave my rMBP on to play things on the hard drive (music, etc.). I'm leaning towards attaching a drive to my Time Capsule and then going with ATV. It's a cheaper investment, and probably all that I need.
Good luck whichever you choose.