Well, it's been a while, but I'll see what I can recall. I fought with them a lot during one project, though it may have been due to a lack of understanding. You can view a bit of that struggle here: http://groups.google.com/group/pylons-discuss/browse_thread/...

The main issue is that they're poorly documented and don't seem that pythonic to me. They are not standard python objects, and as such they are difficult to debug. Hopefully the situation has improved in the past year or so.