I updated manually from 3.2. I'm not rooted. Poke around on xda and you can find instructions. You'll need a USB flash drive and an OTG cable. I don't see much difference so I do think this could be a prepatory update for ICS.
Ya i just installed 3.2.1 and as of now i see really no difference. Stock browser still reverts to mobile for some pages and web pages seem to loading alot slower as droid-life.com took me about a minute to load. Going to reboot and test again.
While reading the update status screen mine said something like "bootloader successfully updated" don't know if that is typical update lingo or thats what the update was doing.
Got the update on my Wi-Fi Xoom... I noticed nothing new or different. I suspect it was for some behind the scenes bug fixes. We use the Xoom in our business for one-on-one sales presentations using PowerPoint presentations... it works very well for that. I also demonstrate our web portal which is flash enabled... again, the Xoom works very well and I have had very few problems.
I'm suddenly getting ridiculously good battery life with this thing on 3.2.1. I haven't charged it since Sunday, it's been on wifi the whole time, and I've used it at least an hour a day. 64%.