In the 737 Classic the aircraft will capture any MCP selectect altitude, level out and automaticly enter ALT HLD mode out of CWS. Additionally the AT will try to maintain the selected speed as much as possible so that CWS is a nice tool to limit your pitch if you plan to release the girls early (ever tried to push a trolly through the cabin at 12° pitch up?). Apart from that i normally don't use it, flying raw data in my company means you're flying completely manual except for AT which is supposed to be in ARM.