I don't understand why people are ignoring the valid point being brought up about the Return to Battlefield issue. In several of the maps with Banshees you can hardly fly very high before you get the same message. This wouldn't be an issue so much if the vehicles were like they were in Halo 3 and were essentially immune to gun fire, but your ship will easily be taken down by starting weapons, sniper rifles, Spartan Lasers, Scorpions, and Warthogs with any turret. The only level that really allows decent height and space for a Banshee is Ragnarok, which is because it's from Halo 3, but it still gets destroyed quickly by the Mantis.
It just doesn't make sense to place flying vehicles in a claustrophobic map design.
I don't think I'd agree that the Banshees can be 'easily' taken down by starting weapons, however this change hasn't bothered me. It keeps players from just taking the Banshee and avoiding the battlefield, and I haven't seen any time where a player with a Banshee just dominates the entire match, like in Halo 3. While I can understand the argument that claustrophobic level design is a poor choice for maps that have flying vehicles, I understand the choices they made and don't have a problem with it.
Personally I was unhappy when I heard they were going to add a CoD style progression system, however I think 343 made some really smart design decisions to keep it from feeling like an unbalanced mess and I'm enjoying it a lot more than I expected to. I'm still using most of the things I unlocked right away without any issues or feeling like I'm underpowered.
The only map I dislike is Exile.
My main dislikes are things like the small QTE in campaign, I'm playing co-op with my wife and it is really distracting. Also I miss Bungie.net. I think the waypoint interface in more convoluted than it needs to be, and there's still not a way to share videos and screenshots taken in the game through it, or Forge maps as far as I can tell. Considering there are achievements for making maps, taking pics and videos, not having a good way to share them yet seems kind of short sighted. No manual, in game or otherwise, is kind of bullshit considering they've made a bunch of changes.
I'm SR21 and digging it. I hope I'm not sick of the maps as much as some of you are by the time I get into the 30s.