I've been buying from Northern Brewer for the last couple of years. It's really *NOT* a good thing that the retail store is only a few minutes off my commute home. And their will-call counter is minutes from my office.
I picked up a cream ale kit from Midwest Supplies last Friday, and brewed it on Sunday. I think I'll stick to kits from NB. For starters, the specialty grains in the Midwest kit were crushed before the kit was put on the shelf. The muslin bag was a little on the small side. I don't need the priming sugar. I also usually use Wyeast Activator yeast, and Midwest includes a dry yeast packet in the kit. I'm reasonably sure it'll turn out good, but I'm happier with the kits from NB.
One other thing to note (and this isn't a ding on Midwest.) When I smacked the Wyeast packet on Sunday, I ruptured the outer envelope! The heat seal apparently was a little marginal, and I lost probably a teaspoon of yeast. The fermentation did take a little longer to get started, but the fermentation lock was bubbly merrily away the next morning.