It looks like the 737-9 varient has an extra set of full sized doors, (obviously a 757 replacement), it does however seem strange that they are located behind the wings rather than in front... I would have thought an extra set of doors at the front could have come in handy for dual areabridge gates...
Apart from that little observation, meh... It's a 737, woo hoo, (it's really hard for me to get excited about a narrow body these days). Besides most of these will make their way into LCC service, so flying on one is not going to be a special event.