We looked at these a couple of weeks ago, we finaly bought a Macnum kit to build. I though the build quality was spot on (especially for the money), the only problem we had were the threads in the motor mounting plate were not tapped correctly so i remachined the mount and fitted csk headed cap screws through the plate to clamp it to the gearbox/diff.
My son has run it a fair bit, a bearing kit will be his next investment and maybe onvert to Lipo to increase run times a bit.
Overall i would say buy one, you can't really go wrong for the money.