A few advices for MT3.0xD upgrades
If you are upgrading your Movable Type weblog from any version to 3.0D or 3.01D, here are a few advices from the trenches:
- If you are hosting it under Apache 2, beware of charset mismatches. MT3.0 now uses UTF-8 as its default encoding (which is good) but Apache 2 backwardly dictates ISO-8859-1 by default (which is wrong)
 - In a freshly downloaded MT3.01D folder, check in the 
lib/MT/Templatefolder for a file named#Context.pm#and remove it if present (its name may cause your FTP server to balk and screw up the upload for subsequent files). I have filed a ticket to Six Apart and this will be sorted out in the distribution packages. This problem pertains only to the current MT3.01D version - If you cannot login after the update with an error that refers to a hash problem (the error message is different depending on the version), delete the 
mtauthcookie listed under your domain and relaunch your browser. This is an old issue 
I hope this helps others to not waste as much time as I did with those tiny but annoying problems.