Alright, I guess I'll update this myself. Someone suggested to me Yak On! through a PM, and having tried it, I gotta say it has the cleanest and most intuitive interface of any of the IM clients I've tried. It also seems to be very stable on my 8700g, on T-Mobile EDGE (I've been on for over an hour without any problems).
However, my feature request still isn't possible, so I emailed Yak On! support, and here's what they told me. Currently Yak On! and most other clients rely on the TOC2 interface to access AIM. This doesn't have the functionality to retrieve away messages and profiles. There is however a second interface, Oscar, which Softcentral plans to use in their next version of their client...which is due to be released sometime next month. This is great news for us all!
Lets hope they keep battery usage at reasonable levels.