I now converted the donations, the stories, the banned users, the whitelist, the Unc-accounts and the karma system from usernames to UUIDs.
Further, I implemented a cascading system that tries to retrieve UUIDs from 4 different sources for a user, namely the blog-registered users, another database to store new users, todays logfile (it registers the UUID of every user that even tries to login on the server, stuff found there is then written to the previous database for later usage) and if all those fail, tries to get it directly from Mojang. I needed to do this since I now need to have the UUID even before the user is registered and if I go directly to Mojang too often, they block me for 1 hour.
There are still a bunch of items left that I need to convert to UUIDs, but there are 2 main plugins that I use on the server (logblock and worldguard) that store important information and so all code that I write right now has to work with both usernames and UUIDs.
I will have to wait until those two are updated and then change all the code accordingly. I assume this should be all feasible before we would be otherwise able to upgrade to 1.8, so this item should not be delaying any upgrades.