Netflix is OK, for direct streaming. The thing with Netflix (again, online only, not DVD) is that they don't tend to have the premium stuff - which is to say that the major network shows/blockbuster movies don't show up on the instant streaming for awhile, if ever. It's gotten a little better over the past year or so, but then again, it's like 8 bucks I think and you can watch whatever you want.
I tend to enjoy a little campiness, and am a huge Anime fan, and Netflix instant has both of those in spades.
Amazon Instant Video I use alot; I am not a Prime member, for no particular reason, but I buy most of my instant stuff from Amazon. I could download it for free from the latest torrent site, but I am conscious of the grand cycle, and I will give my money to support a show/movie/studio/etc I like. Also, Amazon reviews tend to be plentiful, which allows me to make up my mind before I pay money - and, the quality is very good; the HD stuff is in a higher price bracket (way higher), but if you are into that sort of thing, it is there.
Also, you can rent stuff for a decent amount of time (some stuff 1 day, other stuff 1 week) for a measly 3 bones. The selection is massive, too ... rare is it I can't find what I want to watch on Amazon.
I use Hulu for the free stuff; won't pay them money. Also, most of what is on Hulu is on Amazon - and I just prefer Amazon; I will price shop, though.
As always, though, check youtube/Hulu (free) and other video sites before you pay on any of these sites; it's amazing what you can find for free with a little effort.
As to my overall opinion about it, I have basic cable because my dog likes to watch CNN, the Weather channel, etc; the TV's been on for probably five years. I never watch TV, everything I watch is online, sitting in front of my God Machine, otherwise known as a computer. My brother and his old lady don't have any cable, they have a little netbook that streams from the internet to their TV, and they seem quite happy - they watch almost everything for free.