I recently started using Ultimate Bet. So far, I have been fairly satisfied with my experience. Aside from occasional freeze-up, I am happy with the quality of the program. However, Ultimate Bet program did crash on me once at a very important hand. When I rebooted my computer and returned to the table, but program had automatically called a re-raised and I subsequently ended up busting out. When I notified UB about this incident, I got my buy in back (but in the form of a tournament credit which I have since turned into cash). This is in contrast to another site I played on Players Only (which also has an unstable program, but gave me a full cash refund).
The other thing I noticed about Ultimate Bet compared to large sites like PokerStars is the lack of SnG table options. There are only a handful of options, especially in the <$10 tables.
I have not tried to cash out yet from UltimateBet so I can't comment on how efficient they are.