Re: buddypress +multi-db issues
Actually, it would be the other way around. dbDelta is actually a wordpress function that plugins can call to get upgraded. Andrew mentioned that this would all be sorted out with a plan to address buddypress by the multi-db 2.8 release. The reason you have to comment out all the dbDelta lines of code is due to a compatibility error that will fill your errors logs
As well, the search breaks with multi-db since it needs to call more than 1 database since one is global and one is for specific users information, it fails. It tries to find a member specific query in the global DB (since that is the one that is called first) and can’t find the info which causes an error.
The multi-db code also puts all user activity tables in the same DB right now (since it can’t spread them around without code to do so), so the only benefit you get is if you need this solution for multiple blogs. It actually created them all in the global DB when I used the move-blogs tool, but wanted to find them in the same DB as main blog. I had to copy all the user activity tables to that DB for it to work. If you start with a fresh install, it will create them in the right DB straight away.
Summing up, by WPMU and multi-db 2.8 and a 1.0 BP final release, it will draw more attention so that the solutions will have a clear goal to shoot for. This is a topic better suited in the Premium wpmudev forums as well I think. Glad to discuss it further there!