I've noticed slow performance selecting/scrolling folders with many items (e.g realtracks demos folder) from within BIAB.
It can be fixed if you choose "get info" (cmd+i) on the BIAB folder in the application folder. The folder then gets indexed somehow , and things go much faster.

Thanks Svenne,
That's a good tip for the Mac.

I'll move it to the Tips n Tricks Forum.