737 (not only NG, but classic as well) has this annoying "Performance Limit Reversion" feature that immediately reverts from V/S to LVL/CHG if airpeed is less than 5 kts than commanded speed and it's not increasing. So no way to select a higher speed to keep the climb thrust and play with V/S to keep approximately the economy climb speed, like you can on the Bus.
What I found out that on 737, CWS P is a very nice way of controlling a heavy aircraft approaching the cruising level - provided you can explain to your colleague in the cockpit that this is an actual mode of the autopilot that can be used in normal operations. And it even reverts to ALT ACQ, like from other modes.