We have 3 Apple TVs, and the biggest benefit for us is ripping DVDs - now all the Apple TVs in the house have instant access to our entire DVD collection without previews, or annoying menus. We're thinking about getting a 4th soon.
I have 2
tvs, and 3 compatible TV sets. The odd one out is in my daughter's room. If we put an
tv on hers, we'd probably never see her again-- hers is the largest percentage of
tv usage in our household. Why? Like
bbeagle, we find the instant-on, smart-resume movie collection extremely convenient, and our DVDs (and "skip/forward" buttons) no longer get worn out.
Netflix also works rather well on
tv, at least from our experience. Then again, we're not so picky that we demand 1080p. Heck, most of our movie library was encoded using HandBrake's iPhone/iPod touch preset, and I haven't heard a complaint yet. (The smaller file sizes allow me to fit more movies onto my daughter's touch, and oh, the joys of not having to lug around and hook up a portable DVD player and "books" of DVDs to get scratched up in the car.)
EDIT: Those of you who are reading this and considering getting on the
tv bandwagon should consider Apple's Airport Extreme router; it takes "Wake On WiFi" one step further. It has a built-in Bonjour proxy that, upon receiving a message from an
tv to get a movie from a particular library on a Mac that's in sleep mode, will wake up that Mac, have it send the file, then allow the Mac to go back to sleep.