Форуми / Cotonti / Support / Updating from Seditio to Cotonti

I think you can get rid of the following plugins:

• autojoiningposts (if this means multiple posts in a row by same user get merged into a single post, this is default behavior of Cotonti)
• leetlogin (same effect can be achieved using template tags and regular login form in header)
• recentitems (comes with Cotonti by default)
• seourls (can be achieved using Cotonti urltrans functionality)
• textboxer2 (in Genoa this is replaced with Markitup, and in Siena its replaced by CKeditor)

The others I'm not sure, but its very likely that there's similar plugins available or the effect can be achieved using templates in a smart way.

Like pieter indicates, it's safest to make a copy of your site in another location first, then migrate that instance to Cotonti. Only if the migration is succesful you can move to the new site. Ofcourse there's a chance that your old site gets updated (new forum post for example) while you're doing the migration, so its possible you will lose those changes (unless you migrate them seperately or you close the site temporarily).