Ok, since I'm trapped here at work while the wife is staying late to study Biochem, I thought I'd use the time to plunge into the MT 3.1 upgrade.
Upgrade process went pretty smoothly. Copied the files from the MT 3.1 upgrade package into my MT directory, ran mt-check.cgi to make sure everything was still ok, then ran mt-upgrade31.cgi. It did the DB schema upgrade and create a couple of new templates used for the dynamic publishing.
Next step was to enable the dynamic archives. Followed the steps in Movable Type 3.1 Guide, which are pretty straight forward. The only change I made was to put the stuff for the .htaccess file into my webserver httpd.conf file instead. Then did a rebuild. Since there are no archives to rebuild anymore, the rebuild process is so much faster now.
And then I ran into my first problem. I use Paginate for my category and date based archives. The Paginate tags don't seem to get parsed when those archive files are accessed though. But, from the MT 3.1 guide, this is to be expected
Please note that at this time, only the standard Movable Type tags are supported with the dynamic rendering option. Existing plugins are not compatible with this new feature, since they are written in Perl and not PHP. If you are seeing errors due to using plugin tags, you will either need to remove the tag(s) or change that template to render statically.
Then I noticed my second problem: no side bar in the individual entry archives. The side bar gets brought in with a PHP include(). A view source showed everything there, but the PHP include() doesn't seem to get parsed by the dynamic templating. Very odd. A post by Phil Ringnalda on the MT 3.1 beta blog indicated it should work. So in an act of desperation, I changed my PHP tags from <?PHP to <?php and surprise! In came the side bar! But inexplicably, this didn't work for another entry that I have PHP embedded into. Perhaps there was something else that I did that fixed the first problem.
So I'm still having problems with PHP embedded in entries. But so far aside from that small issue MT 3.1 looks pretty good. Still need to play with it a little more though.