If you are using the latest version 0.9.2.1, you can enable coin control (Settings->Options->Wallet->Enable coin control features) and put your main address as your "Custom change address" in the "Send" tab. 
Oh awesome!
Maybe I can continue with (the updated version of) Qt after all.
But does this also solve the problem that Light mentioned:
...and you don't mind backing up your wallet every 100 txs...
In other words, if I change the settings mentioned by Domino, can I just write down (in a safe place) my main address public and private key (which would then be my only address, even if I receive change) and not have to worry about backing up Qt after every 100 transactions?