I've been running the AKU 3.2 update on my MDA Pro for a few days now, and thought I would say how it's coming along.
My first impressions of it seemed to be correct, it feels faster and more stable, and it is.
All of the applications I have installed on it work fine, so far. The new IE is much better, not quite Opera, but getting there.
The ability to use MP3/WMA audio for notifications is a godsend, there so much smaller than the equivalent WAV files that you used to have to use.
Also, even if you are not thinking of going to AKU 3.2, then I highly recommend upgrading to radio stack 1.13. Not only is the Bluetooth now certainly more stable (not had any spurious disconnects from my Parrot 3300), but the UMTS network coverage is certainly better, I get the UMTS connection in places that it just never happened before.
On my drive home in the evening I noticed that the network is mostly T-Mobile UMTS UK, where it used to be T-Mobile UK (GPRS).
If you were thinking about the upgrade, I say do it. You won't be sorry.