I have several WP sites, and just finished upgrading the smallest one (wanted to start on the easiest one - in case there were problems). Good news is no major problems with the upgrade.
Adding the static front page option was good. However, I do agree with one of the other posters about the links categories. I liked being able to easily separate my links. But I do agree that most websites and templates did not include coding that made it easy to use that feature. Guess I'll work around that.
But I do have a couple of suggestions. The new login screen is nice, but the text at the bottom isn't very easy to read (not much contrast).
My main problem is that I was really hoping for an improvement to the editing window for writing posts and pages. Several of the websites I manage are for non-profit orgs who need to be able to edit their own stuff and don't have a huge amount of computer skills. Tool tips on the formatting buttons would be nice. I liked the way the old GUI let you switch between regular text and HTML coding. This one seems to work more like an HTML editor. Is there a toggle somewhere that I'm missing? Also, I've had a fair amount of experience with HTML, but I wasn't sure what the tag was for.
OK, I know I've listed a bunch of things here. My main point is that I really think 2.1.2 is not as user-friendly as the older versions were.