It actually has nothing to do with the shop you buy from, and everything to do with what designer you purchase from. Two dresses from the same store ordered at the same time from different designers could arrive months apart. I ordered mine from Cameo & Cufflinks, and it took about 7 months. Star, I'm surprised S2 said 4-6. My second choice dress (Lazaro) was going to take around 8 months to get in. Ginny, you'll have to ask whatever store you purchase from if your designer does rush orders. It's usually around $500 dollars extra (pretty steep). Cameo & cufflinks is having their floor model sale right now, and there are dresses that literally just came in and have only been tried on once or twice that are on sale from 30-50% off (I was just there for my fitting on Thursday).
Also, if anyone needs a bustier, I got one from C&C that was originally $90 for 70% off (came to $26!!!!). Unbelievable. I was going to buy one from Knickers and Lace for $200!