What would be nice is if the message view heading section ( the bar that contains from/date/subject blah blah blah) was static, and did NOT scroll off when scrolling down the message list.

few weeks ago moved from squirrelmail after 7 or more years to roundcube, did not take long at all to customise it, very nice and impressed, its very professional looking, makes SM look like something thrown together by a 12yo on a rainy afternoon, but the above is about the only pet peave  I've got, overall awesome job.