I found AM 8.5 to be extremely unstable; so unstable in fact that I moved over to LW9; I also tinkered with Maya, and will probably pick up v.8.5 just so I and my fiancé can learn it. That said, both Maya and Lightwave are FAR behind Hash with respect to interface, and implementation of features. Maya in particular is very feature rich, but the interface is a dog; Hash is SO much better in this regard. As for Lightwave.. ugh; a memory hog, and it requires two applications, and you can only render in one.
I am hugely impressed with the stability of v13. I crash every now and then, and I would say that PS CS2 or CS3 Beta are definitely more stable (these are, of course, 2D apps), but Hash 13 is among the most stable I've seen for a 3D app. I still save frequently, but I worry less about the random crash or hangup.
If you want to start modelling and right away, I can't say enough good things about Hash. The interface really facilitates modeling. I still haven't figured out how to unlock some of its power, and there are features in Maya and ZBrush that I like, and miss, in Hash, but both those programs have lousy interfaces. In the end, despite having fewer features, I get a lot more work done in Hash than in any other program.
A returning user's perspective.
Arka C.