I'm a Netflix user and I signed up for a 2 week trial a few weeks ago for Blockbuster Total Access.
Here's the problems with Blockbuster:
1. Movies mailed in as opposed to returned to the store take 2-3 days to be marked as received, and a new one shipped, even though they get mailed back to Minneapolis (where I am)
2. Total Access is cool, but in 2 weeks, I ran out of things I wanted to see that the store had
3. Total Access rentals still have the same due-dates as normal in-store rentals, and you have to deal with the lines and lack of available movies closer to the weekend
4. Blockbuster Online won't ship you a movie if it's outside a 2-day shipping radius of you, meaning a movie at the top of your queue, marked as "available" may get skipped for something farther down if the movie you want is only in-stock on the other side of the country
That served as a problem for me, as I wanted a movie that Netflix didn't have, but it was consistently at the top of my queue and "available" but never shipped to me. If I put a movie at the top of my queue, I want you to ship it to me, regardless of whether you do so from Minneapolis or San Francisco.
I'd highly recommend Netflix as opposed to Blockbuster Online if you're looking at an online DVD rental service. You can try out the free trials for both services and decide for yourself, but I think you'll be most impressed with Netflix, as am I and most of my friends.