It's 1:30AM so I'm going to be blunt due to my lack of sleep for these past few days. I'll read your impressions of it tomorrow, but just going to say that Legends was a disappointment to me. The Animatrix mostly worked well, Legends mostly didn't.
Aside from the last episode with CG which captured the Halo spirit pretty well, and not just because it was in CG, the rest of them had awfully cheesy or simple stories. There were no surprises, the voice acting was average which is disappointing considering that Legends' main audience is obviously going to be westerners, not Japanese gamers who couldn't care less about Halo or the Xbox 360.
The one about the Elite and his lover was a massive cheese-fest, I was cringing through the whole thing. Not to mention the actual animation style was unique, but ultimately shit to watch. Just because it stands out, doesn't mean it's pretty to look at.
The prototype mecha episode was okayish, only because the actual mecha wasn't half-bad. I'd love to pilot that thing in a Halo game, though I imagine so would everyone else, and it would be like waiting for the fucking sniper to respawn once someone has already taken it. Everything else in that episode was also just far too plain or cheesy, might as well just leave out that stupid backstory and show us 30 minutes of epic fight animations instead.
Also the one about the girl who has the teddy bear keychain was probably the only one which had even the slightest emotional gravity. Those who haven't read the Halo books may not know this, but when Spartans are created, they are abducted as children to enter the Spartan project. What is interesting is that the child is replaced by a clone so that nobody knows the government is abducting children to make into super soldiers. These clones are far from perfect, and they usually die young, but either way there is no trace left leading to the government. Knowing this, that episode was actually interesting to me to some extent, but not enough for me to ever bother recommending it to anyone.
So Legends has a couple of average at best episodes, but the rest are just plain shit. I might discuss my opinions in more depth on each episode individually some time later, but for now you get a general idea of what I think. Don't buy this on Bluray, you'll feel like an idiot.