I've been using ROKU for two years, mostly for Netflix, Pandora, and TuneIn. Netflix is the only subscription plan I purchase. Started out with Hulu+ also, but cancelled it due to commercials and the fact that they duplicate a lot of Netflix offerings, where there are no commercials. I have DSL with only 6mega-whatevers and typically have a 15-second load time for movies which come in at 'highest' quality by far most of the time; occasionally will have a brief reload buffer during a movie, but that is not the norm. For sporting events, local news and current TV shows, I simply go OTA - that's mostly for sports at this house. ROKU does also offer sports packages, but I've never subscribed to one. I actually enjoy MLB on AM radio, but maybe you have to be a certain age or something to appreciate baseball that way.
I love my ROKU. I get a lot for my $8/mo Netflix fee. I was so tired of paying car-payment size fees to Cable and Sat companies which, IME, don't appreciate your business enough to show up on the day scheduled for installation, and God help you if you have any problems subsequently. They aren't worthy of my money, obviously YMMV.
Like everyone else, I think Netflix should improve their streaming content. I have not used the amazon service because I'm a cheapskate. I have discovered a lot of BBC, Australian, and Canadian TV shows I like via Netflix, in addition to American fare which I often missed episodes of when they were current. Of course, it's also nice to watch a past TV series in its entirety from start to finish which allows you to follow the 'long story' as well as the episodic one.
In two years, I have experienced far less down time with ROKU then has ever been my experience with Cable and Sat. Down time is rare, and when it has happened has been very brief, with the notable exception of Netfix's recent problem, which was not confined to ROKU only, and which lasted a few hours. Was it New Year's? Once every four or five months it'll lock up on me, requiring a ten-second unplug reset, no biggie. About that same frequency, I'll have to reset my modem/router and have learned intuitively to tell the difference between the need for a ROKU reset and a Modem one, but couldn't articulate it at all. Either way, it amounts to a two or three minute interuption every few months.
I have two ROKUs, and the wife and I sometimes use them simultaneously without problems; it is the primary source for our TV viewing, but if you're hooked on watching the latest TV shows and newest movie selections, it may not be your cup of tea - depends on whether having that is worth the price you must pay. We decided it isn't for us.