The first problem is the AIM/ICQ chat bug. When using a multi-user chat on AIM or ICQ, no messages can be sent. You'll get an error stating your message was too long. This was an unintended side effect of merging the work of one of our Summer of Code students. Ivan accidentally removed a line of code that he shouldn't have. Yes, you read that right--a single line of code. Apparently it was pretty important! Ivan restored that line and things will be working as they should in 2.7.5 when we release it.
The second problem is an old one that's come back with a vengeance. This one is an ICQ issue where messages that contain <> disappear because they're treated as HTML tags. This seems to be specific to combinations of Pidgin and other non-official clients. Pidgin recently gained some new ICQ protocol-level features related to formatted messages; some non-official clients, including older versions of Pidgin, don't handle it gracefully. At this point, we've done all we can do about it; the other clients will have to step up and make fixes to handle the messages correctly now.
The next problem is another wonderful ICQ encoding bug. I'm not sure if this one is a side effect of Ivan's work or not, but Ivan did do a lot of work on encoding problems on ICQ. We all thought things were improving, but apparently there are still a few odd cases (and a crapton of stupid ICQ clients that should be purged from existence) in which our handling of encodings just isn't quite right. We're aiming to have this fixed for 2.7.5, but it's not quite done yet.
Is it obvious I wish ICQ would just disappear immediately and permanently?
The last "big" problem that seems to be cropping up is a crash related to MSN file transfers. When using direct-connect file transfers, somewhere along the line we do something stupid internally that causes a crash. We thought we had it fixed for 2.7.4, but alas it still exists. We're looking into it and hope to get it fixed soon. In the meantime, it's pretty easy to prevent the crash--edit your MSN account and turn off the direct-connect file transfers. It's an option on the advanced tab of the account editor.
At any rate, since we know about these bugs already, please, please, please DON'T open new tickets about them!