I have BFD though only the basic version with 7 drum kits plus some extra snares and cymbals. It's great. I guess it is like having a real drum kit miked up. You can change mic distance etc. and easily set up the kit for special effects on part of it.
As to samples I have some from Sonic Implants. Their basses are great. I also have their Session Drums which sound okay when running a karaoke program or something like that through the sampler. In this situation you can't always have more than one midi unit attached, so BFD won't do.
Finally I bought 6 cd's cheap off eBay with what I guess is free samples. You can, of course, download these from various places on the net, but the guy ordered them into groups like organ, guitar etc. and collected it all.