hI mARC1
Since we received a message on the users list about this, I made some comparisons between 2.6.0-pl2 and 2.5.4. I am quite surprised to see 2.5.4 being 3-4 times quicker in routine operations like cookie login, changing db, going into Structure page for a table, etc.
Did you compare some special URLs? I just ran xdebug over the left frame and found it spends quite a lot of time in fetching Bookmark information for every table (pma_querybookmarks()). That should maybe be optimised to always fetch all bookmarks of a database and cache the result in a PHP array.
Regards, Garvin.