It's awkward to get in and out of the seat, which is unfortunate with some of the longer legs (pilot's and aircraft's). FO's bag goes in the main cabin, and actually behind First Class on the -900... annoying at the times you are trying to go reverse flow. Lav and water status indicators are conveniently located at the back of the airplane. Overhead panel, even on the newest 737, hasn't advanced much in decades. The noise can be mitigated by a good anr headset, but the good anr headset can be mitigated by a captain who would rather yell (or worse, mumble) and listen to the overhead speaker. Intercom use seems to be increasing slowly. The airplane is happy to overspeed itself if you aren't paying attention. The trips and layovers are generally some of the best in the domestic system. Some aspects of the avionics are great and others are a little quirky. Captains seem to love the hud. If you like saying goodbye, it takes a long time to get all the passengers out, so that's nice.