I just picked up rollers at Interbike after trying them out. The Kreitler folks were really cool- I got there early, they got me mounted on the bike, then instructed me and held the bike until they slowly let go (without telling me). The key was that they got me to relax and keep a light grip on the bike and to keep a good clip (at least 15 miles per hour). Doing that, I was able to stay upright and build up some confidence.
I will certainly practice in a door until I get the hang of things, and worst case scenario, I have that bar to put on the front of the rollers to help me get used to the idea of mounting and dismounting so that I don't kill myself in the process. I'll be in the hallway for a while, though.
Koffee