It might be too early to tell, but I believe this solved the two biggest problems I had with roundcube. It solved the problem where the new mail display in the inbox would increment but it would not show the message. Ie, INBOX(1) but a new message would not be displayed (as noted by the previous posters).
It also solved a problem that I thought was related to my IMAP server. Every once in a while, when I logged into roundcube, or refreshed the page, it would say "No messages available." or something of that nature. I would hit F5 and it would then display all of my messages. Additionally, when I double-clicked to read an e-mail it would sometimes time out. Hitting f5 would display the "No Messages.." prompt, and refreshing again would fix it.