I go to Blank's mostly for upholstery supplies and to at least look at their upholstery fabrics. They have tools and materials that Joann's employees can't even identify, let alone stock. Some of the fabrics are very high quality with steep discounts and their selection of neutrals is especially nice.
Their upholstery foam is much better quality than the stuff you get at Joann's and i think is lower in price, plus their selection of sizes is greater.
They have a lot of garment fabrics too and their special occasion fabrics are supposed to be good but I haven't been able to find what I want there yet. It's worth a look, though.
Service is very iffy. I've asked for very specific things and was told they don't carry them and then I found the stuff on my own in the store. Some employees are nice but the older gentlemen (owners?) are not very friendly and do not go out of their way to help.