I've successfully got 2.5 working locally, however when I migrate to my server by
a) exporting the database and uploading to my server
b) updating wp-config.php with the correct details
c) uploading all files
and d) changing references from my local install to my online install
I get the following error when I visit the online WP-Admin:
Fatal error: Cannot use string offset as an array in <my online site>/blog/wp-admin/includes/dashboard.php on line 46
I note this does not happen locally. I downloaded my old 2.3 to my local server to do the 2.5 upgrade.