Two separate requests:
Most importantly - there must be some better way of dealing with large maildirs. I have over 25,000 messages in some folders and Roundcube is SOOO slow. Improving performance w/ lots of messages is my main, most important request.
Second, I would like to request that roundcube display the number of unread/new inbox messages in the title bar like Gmail does. Actually, I was surprised this feature wasn't there, so I'm sorry if it's already on the list of requests and I just missed it.