I have been purple since the beginning, but that first year of Blu-ray was pretty rough; making me a bit more reddish.
IMO: HD DVD has made Blu-ray a better format. It pushed studios to create high quality video encodes, abandoning the antiquated MPEG2 format. Once the bulk of studios went VC-1 or MPEG4, Blu-ray encodes started to become some of the best in high definition available. With movies like Pirates boasting bitrates higher than those available on HD DVD.
For audio Blu-ray has almost always delivered. With Sony, Fox and Disney having 100% of their releases in lossless audio (even if only about 12 of us can hear the Fox tracks).
Special features it's not contest; HD DVD has dominated this arena, but now with profile 1.1 Blu-ray has once again caught up in another area. I personally love the PiP features, but if I can get those on Blu-ray with high quality video, than there is no reason for me to be upset.
HD DVD has most certainly helped lower HD player prices across the board. Boosting sales and enthusiasm for both formats. And feature-wise HD DVD delivered a solid standard of TrueHD decoding, internet connectivity, standardized HDi support and firmware updates that would often dramatically improve performance.
HD DVD may end up the martyr but I feel it's done a world of good for high definition movie watching as a whole.