-I tried importing a Psion, it did not work (but I know you mentioned it probably wouldn't)
Yeah, I'm not surprised at all by that. I've never tried to figure out how psionics might be supported as we've never had a psionic character in any of our campaigns.
-I tried some combat with imported PCs and NPCs, it threw an error: Unknown library token Lib:Blakey. I fixed this by bringing the Lib token to the same map I was fighting on.
As far as I'm aware you should be fine as long as you have that token on any one map in yuor campaign. And make sure you don't have multiples as I believe this can screw things up.
-I noticed the PC tokens were set to NPC, so I changed them to PC. After that, the Character Sheet didn't work on mouse-over, so I put them back to NPC. This, unfortunately, seems to mean I can't use the Vision Blocking Layer to separate what the PCs see from what the NPCs see. Is that something your group does not use?
We do use this, yes. What you need to do is make all the PC tokens PCs as you first did. Then in order to pop up the PC character sheet get them to select the PC token and press F12. This is the key which is used to pop up PC tokens.
If you enable the "Selected" window in MapTool you'll see a macro on each token - one for each power they have and at the top in blue one which is labelled "Character Sheet (F12)". That's the macro which sets up the PC charactter sheet and it's fired by pressing F12.
This means the DM and the players use slightly different ways to use tokens - the DM uses mouse over and the PCs use F12. You could easily change this by changing the Campaign Properties about if you know what you're doing...
-The Monster I imported does 2 Ongoing damage on a hit. While I can put the Ongoing Damage state on a token, is there a means of noting that it should be for 2 damage? How do you guys handle that?
We just remember it. If we need to remember it from session to session, we stick a note on the token Notes field.
-If I can't import a character, is there no way to manually build one? Create the Powers, etc?
Not easily. but as I said, if you enable the "Selected" window you can see what you are trying to build. You need to fill in all the Properties on the token, and then you need one Macro for "Character Sheet (F12)" which you could copy from another PC and hack - although you'll need good MapTool-Macro-Fu to do that. The other tokens are for usable powers and all they do is pop up the HTML in the "Compendium" frame so if you have the rules easily to access suring a game you don't really need this part.
What do you think of the framework overall?