The "some free DLC" is the Halo 3: ODST campaign, so it's definitely something worth specifically noting. I'm glad they're doing it because I never played that game on 360. I'm not sure how the month of LIVE and other stuff is acquired, but they said that the ODST campaign will be out in the spring, so maybe the other stuff comes with that.
The matchmaking has definitely improved, though it's imperfect. Many playlists are still missing, and I honestly don't even know that any Halo 4 maps are in the multiplayer rotation (despite trying Big Team Battle and SWAT, both which claim to have Halo 4 in the playlist, I never saw a Halo 4 map show up in the lobbies). However, connection times are way down, and most games are stable. I'd probably say it's at a 7/10 state right now, as there are still issues with team balancing and prolonged sustainability.
I haven't tried any online co-op campaign play in a while, so I can't say if the lobby/party issues from that are any better.