Yes, the Ideas forum is run on bbPress, but it's version 0.9.0.4, not bbPress 1.0 (the backend looks like WP 2.5, not 2.7, and doesn't have some of the functionality that was added by Sam Bauers in the later development stages). Also, the plugins that run it are combination of hacked support forum stuff and original code (ratings, etc). There are a number of issues that need to be fixed. The one that makes it seem broken is that the ratings plugin doesn't interact correctly with the other plugins, so things show up as most popular even if the thread has been closed, relegated to plugin territory, etc.

There are a number of other, smaller fixes that need to happen, and I'd like to clean up the design of the front page and the 'ideas you haven't rated' screen so that there's more consistency and it's easier to scan ideas based on category, etc. (Oh, yeah, 'ideas you haven't rated' doesn't care if the thread has been closed, either.)

I have a list of fixes, but no one with time to tackle them yet. If there are any bbPress gurus reading this who'd want to help out and get Ideas into fighting shape, shoot me an email.