I am running a home server with an rt73 usb stick which enables Internet connection sharing over wifi. I've been using the legacy driver in ad-hoc mode with WEP for a year now. I tried the new in-kernel driver a few times, but I was hitting various problems which prevented me from switching over.
A few days ago I loaded a kernel with the driver version 2.3.0 from Ivo van Doorn's git tree. I've been running it for 4 days now without any problems. More than that, it seems that the range of reliable signal reception has increased compared to the legacy driver. It could be the new minstrel rate control algorithm or I'm just jumping to conclusions I have no hard data.
Anyway, many thanks to Ivo van Doorn and other contributors! I am definitely staying with the new kernel. Thank you for your hard work!