I'm running the new 9.0.5 (with Lion Beta compatability).
It's been working great. I did a full clean install and whether it's because of that, or because of Lion and the new 9.0.5 things have been stable enough. I haven't fully stress tested it, but it has been running without a hitch so far.
I had been having a lot of problems with Pro Tools on Snow Leopard for some time, which is one of the reasons I wanted to make this jump sooner to see if things would improve, and so far they have.