I've purchased three sets total through Weathertech and KB Car Stuff. Both were prompt and I had no problems. Weathertech's pricing is usually MSRP with no discounts and no free shipping. Sometimes you can find a discount for KB Car Stuff. I'm sure there are other retailers that sell weathertechs, maybe others can chime in.
As for the fit, they seem to be pretty good. Some parts don't contour to the side paneling, but I really don't find that to be an issue. Others have had weathertech replace them but I believe they were extreme cases.
Take a look at Husky liners as well. Many people have them on here and they do the same job at a cheaper price.