I have bought a baybus from pcmods.com and was very happy with their service. I happened to recieve one that was part of a mismanufactured batch that they found out about after some had shipped out. I e-mailed them about it and recieved a prompt response giving me an RMA #. My only complaint about the entire thing (I'm not really even mad about getting a bad one, can't expect them to be perfect) was the fact that they make you return the old one before they ship the replacement, I don't blame them for having this policy at all since many companies have had to take this step to prevent losses, but it still would have been nice to have the new one in 3 days instead of a little over a week and a half (took me a while to get the old one shipped back). I think that their customer service department is very good and their products are excellent from what I have seen and the reviews I have read.
VH has done reviews of many of their products including the window kits I believe. Overall I would give PCMods an excellent rating especially when you consider what some of the other small companies on the net are like.
Eric
edit: forgot to mention they also have the option of cross ship, where they charge you for a new one and then refund it when the old one gets there.