If not a horror story at least a sad story. I bought 8 (1000 watt) ballasts from HTG supply. Over the first 3 months I had 4 burn out. I called them and they sent replacements. Within 3 more months the other 4 originals had burnt out. They sent 4 replacements only these were old and battered POS`s. They lasted about 1 month. HTG supply stopped answering the phone when I called. Within 2 months I did not have 1 working ballast.
Luckily, My local shop is staffed with great people. Each time I would loose a ballast, the shop would let me use a loaner until it was replaced by HTG supply. As HTG supply became more surly and then unresponsive, I bought new at my local shop until I had replaced the whole set up. Since then I have had 2 ballasts burn out - both replaced with a loaner and sent back for repair within hours.
What the whole experience taught me was that you may save some money buying from someone non-local,( in my case 3000 miles) when it is time for your lights to go on, it sure is worth every penny to know they will.