I only enjoy watching commentaries on very few movies--ones that have so many awesome practical effects and are spoken by people who really have a lot of inside knowledge, neat little factoids, and can tell them all in a really interesting manner. (Case in point: Bruce Campbell's commentaries on the Evil Dead trilogy.)
What bugs me is when a company strips away a few things when making their Blu-ray release of a movie they've already done on DVD. Specifically what I'm referring to is The Stendhal Syndrome. For whatever reason, Blue Underground's BD doesn't have an original stereo mix of both the English and Italian tracks, when there are such mixes on Blue Underground's DVD. For whatever reason there's TWO 7.1 mixes, which seems absolutely absurd to me. I want the stereo mixes, as well as mono mixes of films that were originally in mono, and I want them to be lossless. With the size of the discs, there's no reason not to have them; two 7.1 mixes are redundant and a huge waste of space when they're virtually identical.