I managed to find and complete perfectly all 3 MP matches I tried to join yesterday night, Halo 2 Anniversary playlist.
Everything was flawless, actually. I had a blast, 60 fps makes all the difference.
Bit hard to get back to it after playing Destiny so much, specially the lack of a sprint button, but of course it becomes second nature for anyone who grew up playing system link Halo CE and 2.
Didn't have any connection problems whatsoever. After 3 matches, tried coop CE campaign, and noticed a small delay (measured around 0.3 seconds). Not unplayable, but not flawless either.
Anyone, having a blast so far. Best collection/remake by a long shot.
Edit: Halo CE looks horrible, really. Had way more fun doing original graphics. I didn't find particularly impressive on the 360, but nowadays is simply terrible from an artistic point of view. Do yourself a favor and play the campaing with the original graphics.