I have installed about 6 sets of DDM Tuning HID's, but the quality has gone downhill. I have switched to VVME. Much better price, faster shipping, and quality parts.
I put the ddm lights in my Mazda beginning of this year and I do have issues with the pass light not coming on sometimes. Ive had them in my mustang and Sierra for several years without any issues. I just put some xentec lights in my R1 and I'm happy with them so far. They were $30 shipped from eBay.
I've had to replace ballasts under warranty a couple times with DDM for my Sierra or wife's Jetta. I have them as low beams and fog lights in both vehicles and used them on cars I've sold. I won't knock DDM too bad because for the most part they are a decent product. I've just had a couple headaches because of them.
I've used about 3 sets of the VVME's and haven't had any issues so I am going to continue using them.