Hey Graham. You guys are doing an excellent job. I don't think this has anything to do with you guys at all. It's just that IMO a lot of people were used to the ease and functionality of the old phpBB boards. Then they come back to find out it's changed, it's slower, there much less functionality, and oh yeah - you have to re-register.
Matt and Mark have made some very good progress and things are much better now (although I still miss phpBB), but in the initial startup I think we lost a few people.
Absolutely nothing to do with what you guys (the software engineers) are doing, or haven't done for that matter.