I took the plunge on my research blog and upgraded it from 2.05 –> 2.1 today. So far so good. The other blog is quite a bit simpler and uses far fewer plug-ins, of which I remain trepidatious, but we shall see how it goes.
On the path of searching out any hurdles that others had run into, I came across a series of blog entries by Alex King when he re-invented his main blog last year. These posts are a wonderful case study of his systematic approach to usability and user experience with his own blog. he is well known in the blogging community for his theme contest and his website which relies on WordPress for its cms is impressively extended through a few other pieces such as his forum management, but all nicely integrated together. I point out this post as a great resource for wordpressers or wordpressers to be that may like to be reminded of those usability things to remain aware of.