Absolutely. The only problem I've found is that they tend to sent their orders in little bubble/jiffy bags which the postman sometimes has great pleasure in destroying at the sorting office so you might end up with a dented book. My copy of The Fountainhead for example, turned up with a slightly abused spine which miffed me a little. That said, it's nothing to do with BD themselves and all to do with RM.
That said, if you don't qualify for the free-delivery elsewhere, they can be much cheaper. It's best just to shop around really, but I've snapped a few bargains from BD thus far.
For example, Cormac McCarthy's The Road (which we have discussed in the book-club) was purchased for the grand sum of about £4. Bargain.