I use a couple of different labs depending on what Im doing. Locally I use BWC for real black and white fiber prints, and hand color prints. Then I use WHCC for a majority of the rest. Im currently trying a new process for my underwater images by having them printed on specially coated aluminum.
I avoid sams and costco like the plaque as I havent been able to get any decent results from the local ones even with the "autocolor off". I suspect this is due to them not maintaining there machines like they should. Then there paper selection isnt that great, I like gloss papers (endura metallic, and endura portrait papers).
I wish Illford would finish up the the R&D on digital fiber paper as when it comes to B&W images nothing beats a selenium toned fiber print