I've tried to install my old 1.1.x theme on the new 2.0RC1 Version.
It seems to work fine mostly, but some descriptions don't show up.
After looking one of them up in the RC1-default theme, it seems to me that $txt['welcome_guest'] has changed into $txt['hello_guest'] now.
Is there a list somewhere? That would make it easier for me to fix my theme.
In the sources directory of your install, look for a file named FixLanguage.php. It has a complete list of the old naming conventions and the matching new names.
I had the same issue where the upgrade wasn't able to clean this up.
Good luck,
A
You can also use this site to check the 1.1.x value and then 2.x value:
http://huw.org.uk/smfstrings/