At least you can still get AIR for OSX. Trying running the HipChat client on Linux... it's pretty painful, and getting more painful as time goes on (and we get further and further from Adobe's last release of AIR for Linux). It's even more painful to get it running on a 64 bit Linux distribution...
- AIR doesn't play nicely with dynamically switching graphics chips (read: all MacBook Pros and iMacs). The app itself, AIR's installer, and updater, will all randomly crash due to this, with no hint at what's wrong. The only way to fix this (if you've somehow realized this is the problem) is to lock your graphics card in System Preferences.
- It will peg your graphics card, just like Flash on Mac. You can be looking at a plain chat window and hear your MacBook Pro spinning up like a jet engine, as if you're about to do something, well, more substantial.
- It crashes, and worse, it has a really bad habit of corrupting itself when crashing. To-date I've reinstall HipChat at least 10 times on my machine. The "AIR installer crashes randomly because of graphics card problem" undocumented bug makes this even more annoying.
- It's just slow.
johnnydoe is right. AIR is like client-side Java, or any other write-once-deploy-many products. It's lowest-common-denominator crap. It has all of the limitations of its target platforms, none of its strengths, and all of the laziness that comes with trying to design a one-size-fits-all UI for everyone.
Also I hope HipChat will now finally get that native OS X client they've been promising for ages.