With the release of the fifth Harry Potter movie, they reissued all of them in HD (Blu-Ray and HD DVD). Seeing as how I didn't see the first three in the theaters, I figured what the heck, I'll get the box set. Plenty of HD eye candy there.
I put the first one in while I'm doing other things, because it was also just on cable, but it's funny how I look up and see detail I never saw before. For example, the "gym teacher" who teaches broom flying has yellow eyes. Would've never seen that in standard def.