I picked this up at a local CD shop a few weeks ago and I'm pretty impressed with it. There are a lot of reprises from the first three albums, but it's a very solid listen. As far as favorites to, I can't get enough of "Infiltrate [Sierra 117]" and "Three Gates [The Covenant" (especially the first two minutes or so). It's nice to see that HALO music has evolved a bit but still retains the classic elements that made the OSTs so enjoyable for me in the first place. If you dug the other HALO music thus far, you should definitely grab this 2-CD set. Just ignore the last track on disc 2 - it's some "bonus" track from some band that won some contest; obviously very important.

Meh. Couldn't get myself to liking this at all.
I LOVED the Halo 2 OST and was really looking forward to 3, but I found it really disappointing...

I agree.  Halo 3 OST was basically a re-tread of Halo 2.  There were some new songs but it just didn't have the same impact.  I own both Halo 2 OST's and Halo 3 OST.  The tracks you named were awesome though, especially "Three Gates".  The staff/roll song is awesome as well.