The nine maps are excellent, not as good as Lockout or Headlong or Midship, but still very good...
Turf - My favorite map from the map pack, a very balanced and cool map. The best from the pack IMO.
Sanctuary - My second favorite map, well balanced and very fun to play snipers on.
Backwash - A cool swamp based map. But the 360 lag problem keeps me from playing on it. Well balanced and is the only map with a Sentinel Beam.
Containment - They should have just remade Sidewinder, too big to play anything good on, except for maybe Gulch Wars and Hog Wars.
Warlock - Not the most balanced, but a remake of a better Halo: CE map, Wizard. TOO MANY BATTLE RIFLES!
Relic - I hate this map, if you aren't a sniper person, you suck on it. Not to mention all the good weapons are in the base.
Gemini - Very cool map, but a lack of medium range weapons makes it hard to play on, too many close range guns and the beam rifle.
Elongation - Alright for CTF and Oddball, not fun for Slayer...A remake of the map from Halo: CE, Longest.
Terminal - Ughh, this map is bad, not horrible. It's just better for Assault or CTF, not a game like Slayer.
Now for the videos, Another Day At The Beach just explains what happened to a dropship that crash landed on Earth. Killtac. is about the new maps and give a back story to them.
This is a sure buy if you don't have XBL, if you have XBL, download them.