I just finished the third level. I don't know if this is a personal error or not, but the worst thing I've experienced so far are the cut scenes.  They are very laggy and pixel-y as hell.  The gameplay and story seem to be going well though.  I didn't know how to melee for about half an hour and kept smashing the B button until I pushed the RB out of curiosity. Then I discovered the button layout had changed completely. Maybe I should have leafed through that instruction manual.  Also, personally I find that pushing the LB to spring is incredibly annoying, but I understand the limitations of the controller.  After playing so much Call of Duty Black Ops lately I also found myself wanting to crouch all the god damn time.  These are petty personal gripes though and the game seems to be shaping up to be fun. Looking forward to the rest. 

I just finished the third level. I don't know if this is a personal error or not, but the worst thing I've experienced so far are the cut scenes.  They are very laggy and pixel-y as hell.  The gameplay and story seem to be going well though.  I didn't know how to melee for about half an hour and kept smashing the B button until I pushed the RB out of curiosity. Then I discovered the button layout had changed completely. Maybe I should have leafed through that instruction manual.  Also, personally I find that pushing the LB to spring is incredibly annoying, but I understand the limitations of the controller.  After playing so much Call of Duty Black Ops lately I also found myself wanting to crouch all the god damn time.  These are petty personal gripes though and the game seems to be shaping up to be fun. Looking forward to the rest. 

" I just finished the third level. I don't know if this is a personal error or not, but the worst thing I've experienced so far are the cut scenes.  They are very laggy and pixel-y as hell.  The gameplay and story seem to be going well though.  I didn't know how to melee for about half an hour and kept smashing the B button until I pushed the RB out of curiosity. Then I discovered the button layout had changed completely. Maybe I should have leafed through that instruction manual.  Also, personally I find that pushing the LB to spring is incredibly annoying, but I understand the limitations of the controller.  After playing so much Call of Duty Black Ops lately I also found myself wanting to crouch all the god damn time.  These are petty personal gripes though and the game seems to be shaping up to be fun. Looking forward to the rest.  "

Some scenes loaded a little later then others, showing ugly textures for a small time but nothing major.
 
Also be sure to check out the different control settings they have (including a image showing button uses) in the options screen.
I went with Recon, which is kinda what all previous Halo's were like.

If you don't like the control options you can change between them in the start menu. Also, while the cutscenes don't always have a perfect frame rate you shouldn't be experiencing any lag or pixelation, it sounds like that may be an issue with your A/V setup.

" If you don't like the control options you can change between them in the start menu. Also, while the cutscenes don't always have a perfect frame rate you shouldn't be experiencing any lag or pixelation, it sounds like that may be an issue with your A/V setup. "

To everyone: I did add the caveat that these were all personal gripes. I understand that I had the option ro change the controller scheme. This isn't my first rodeo.

I think I changed the controls to Recon as they seemed the closest to what I was used to from older editions. I never noticed horribly laggy or pixelated cutscenes though.

Having AAs assigned to LB is key so you can aim while jetpacking.  Reach's scheme is very similar to Halo 3's bumper jumper, just with AA assigned to LB instead of jump.   I do miss being able to strafe/aim/jump/shoot without moving any fingers.
 
I don't play much COD, but I'm sure I'd have a lot of Halo habits causing annoyances with that game.