I like the fact that the carry many different manufacturers of the same part. Rocks descriptions are good making it easier to get the correct part. Whats really cool is they offer kits, for ex. They offer a brake kit that has 2 rotors, pads at a reduced price.
The cons are: if you order a few different parts, they come from different places and each place adds shipping.
Tricks, you can get an oil filter for $2.5, but 4 bucks to ship, so order 4 at a time, this works well for items that are small and lite.