On the mac, at least, I've found the AIR client is really, really good. I haven't really run into any of the issues you mentioned and have been using it daily for several months.

And my coworkers really love the web client. And some use xmpp. Many of us regularly use the iOS app. I guess that's one of the strength's of hipchat, the variety of access methods that all feel basically first-class. (and one person on our team even uses the SMS integration.)