This, plus a pretty unique system for allocating cash around. Perhaps it's psychological, but I've been with them for about 3 months and have started burrowing out of a years-long financial hole in pretty short order.
Basically, imagine the envelope budgeting system as an actual part of your account, combined with a daily savings option. Assuming that you enter your bills in correctly (and it's, erm.. dead simple), you know immediately how much cash you have is safe to spend.
Great CS as well. Actual humans who speak English and who can solve your problems.
Can't recommend them enough.