My usual response to 'Welcome aboard, how are you?' is (smiling meanwhile)
'All the better for seeing you!'
Be nice to CC and they'll usually be nice to you.........
There's one America West ground agent at San Diego who always has a problem checking me in with my international multi airline through tickets. But by being nice to her, it ends up with her asking the CC to look after me especially because I didn't complain! And they normally do, too.