I just recently had a bad experience with Canada Computers.
Went in to buy a system before Christmas, came as a bundle package. Case was hideous, so I asked to swap it out; no problem, just pay the difference. Bundle didn't come with a keyboard or mouse, so add those to my bill. Windows XP? What the hell, it's a free upgrade to Vista. Also bought a second system as a gift for my brother and was able to pick that one up immediately.
Magic number for a build time for my computer, two weeks. I didn't need it before Christmas and knew they were busy, so whatever. Two days before the due date, get a call from them. They can't get the sound card in but are willing to swap it out with an equally impressive sounding one for a few dollars more and it'll be ready a few days late. A week later, get a call to inform me the mainboard isn't available through them and describe an alternative involving most of the Polish alphabet... for a few dollars more and a few days later. A week later, another call. No power supply, but for a few dollars more and a couple extra days...
I remain calm and do so math. So far, this has added up to an extra 10+% on the original cost and two weeks late. So, I walk into the store and cancel the order. The manager wasn't available to discuss refunding my deposit, but if I could just wait a few days, they'll look into it.