Fictionwise is my favorite bookstore and has been for years. (Since they were very small publishing mostly short stories). As you've found if you have a problem with their books or even software they are quick to help out. (In my case they even sent me an old version of Ereader Pro I bought waaaay back because I just plain liked it more!)
They have the best selection for multi format books, and if I do buy a DRM book I always use their format as it's the most portable for my selection of devices. (WHich does now include the blackberry!)