For what it's worth, I have Netflix and it's great. It doesn't take 2 days from the time they ship it. Rather, it only takes 2 days from the time I drop it in the mail. If I return a movie on Monday, I have a new one by Wednesday. Can't beat that. Plus the selection is better than Blockbuster for a lot of foreign films and anime. And I love the Netflix website. They only do one thing, and they do it extremely well.
I've never actually used Blockbuster online, but I like the idea. I may still give it a try. I expect the turn-around would be equally short with them. I live in DFW, and I think it's the corporate headquarters of Blockbuster.
For anyone with a Blu-Ray or HD-DVD player, you'd be crazy not to have such a service. Those discs simply cost too much to go out and buy. Yet renting them online costs the same as regular DVD's.