I have been buying books (and other items) from them since I first came online in 1997. They may not suck all the time, but it's just that they are now so inconsistant and unpredictable. (And the fact that they use UPS almost exclusively doesn't help matters, but don't get me started on UPS.)
Now it is a roll of the dice to order from them. Your milage may vary.
I should say, however, that I browse their website quite a bit. I like to read the customer reviews before I buy books.
That's something brick and mortar stores can't offer.