I <3 my Roku boxes.
I still don't really get the Netflix backlash, because you're still paying a tiny, tiny monthly fee in comparison to what you'd be paying per-watch for anything else. I think it'll be much more cost-effective to stay with Netflix, but it depends on personal tastes.
Hulu is an excellent tool for catching up on new episodes of TV. I don't use them for watching older shows; their library is odd and doesn't really hit that "just missed 'em" section of time for TV shows. Hulu offers you brand-new stuff and ancient stuff, but not a lot in-between.
Amazon Prime just announced today that they had finalized a deal with Fox to bring
24,
Arrested Development,
The X-Files, [i]Buffy the Vampire Slayer,
The Wonder Years, and more to their streaming service (also viewable with a Roku).
I don't have cable, because I have these other services (Netflix, Amazon Prime, Hulu Plus). My basic media plan is:
Watch what we can through Hulu Plus.
Shows not available through Hulu are picked up with Amazon Instant Video or iTunes purchases (
Doctor Who,
Supernatural,
Warehouse 13, etc.)
Shows for which I can wait until the season is finished get a watch on Netflix once they're released (generally just in time for a new season to start).
All of this occurs via my Roku (aside from the iTunes shows; see below).
Personally, because I'm in an exclusively Mac environment, the Apple TV is a great machine for me; I use Handbrake to rip old DVDs and throw 'em into iTunes, then just stream them with the Apple TV. Saves tons of space and hunting through 2000+ DVDs. The good thing about iTunes purchases is that I get an actual file in addition to streaming; Amazon Instant Video doesn't offer that option for Macs.