Last Friday Warner Bros. dropped a bombshell, announcing they will release high definition movies exclusively on Blu Ray. Warner had been carrying HD DVD, Blu Ray's rival format, for months with titles such as 300 and Blood Diamond, which have more features than their Blu Ray counterparts, and their superb Matrix box set. This leaves Universal and Paramount as HD DVDs lone supporters, while Blu Ray has Warner, Fox, Disney/Buena Vista, Lions Gate, and of course Sony in their stable.
On one hand, I just bought a 2nd HD DVD player about two months ago - a Toshiba HD A3 for about $104 shipped. On the other hand, I just sold my 1st HD DVD player, an XBox 360 Add On Drive, for $135 last month. If you can get a dedicated HD DVD player (i.e. not the Add On drive) for under $150, it's a decent value as a DVD upconverter and occasional player of HD DVDs.
If you want to know the difference in the formats beside support, it basically comes down to this: HD DVDs are capable of displaying picture-in-picture (Or PiP, clips from featurettes can be shown in a picture in the corner during movie playback), while Blu Rays are larger and scratch resistant. The larger size of the Blu Rays, in some cases, has led studios to put a second cut of certain movies on the discs with the PiP commentary.