I support HD DVD over Blu Ray for a few reasons.
First, I enjoy having the extra Web content in movies. Like in Transformers - during certain scenes, you can access Web content that gives more in-depth look at items, more than the director's commentary can provide.
Second, I have been importing VCDs for years - and not having to worry about region coding thrilled me. I haven't bought any foreign HD DVDs yet, but planned on it when the price came down enough. And besides, I can get quite a few BR titles on HD DVD overseas.
Third, I wasn't impressed by the pricing of the HD players. When I was able to get 9 free HD DVDs and a $99 player, I had no choice but to hop in.
Lastly, I am not thrilled with the prospect of buying into a format that is still trying to find its way. That would be Blu Ray. They are still trying to implement features into their players that are standard in HD DVD players. And I could care less about the storage capacity. It can all be changed with a firmware update.
Do I plan to sell my 360 add-on or HD DVD player anytime soon? Nah. I enjoy it thoroughly. I also have no plans to go Blu unless I buy a 60gb PS3 with full BC. That is the only way I will go Blu soon. Maybe if there's a $99 BR player, but that is quite a ways off.