I've merged in most of the reset related fixes from my git tree into FreeBSD-HEAD. This means that normal resets (eg stuck beacon, calibration resets, etc) shouldn't drop frames any longer.
Frames are still dropped during things like channel/operation mode changes and channel scanning (which does do a channel change.) I'll have to look into that at a later stage. If you're using this in station mode you will likely need to disable background scanning or your aggregation sessions may occasionally drop. You'll have random messages logged when frames are dropping during a flush or reset, so just check your system dmesg log for anything from the ath driver.
I'll be next working on correctly handling failed/filtered frames and then adding some transition stuff to net80211 so the TIM/ATIM bitmaps can be kept correctly up to date. This should fix some of the power saving issues that I'm sure exist.
Unfortunately transmitting BAR frames is still quite a bit off. There's a lot more tidying up that I'd like to do before I start down the path of handling BAR TX, including trying to figure out how to better handle packet transmission and reception when the NIC is off-channel (eg when doing a background channel scan.)
I also have a long list of things I'd like to do to the rate control code and all the surrounding code which sets up rates and creates aggregates. The code I ported/wrote is a little too verbose and duplicate-y for me. That likely will occur after the christmas break.