I've also felt that way— and when I feel that way I use signmessage/verifymessage exactly as you've suggested. (I'd say— use a raw transaction, but you can't really do that until you have coin assigned to that address). Doing so shows that there was no crazy cosmic ray induced insanity with the key generation.

The people who've assigned very large amounts of coins to single addresses, or even single outputs— I think these people are insane.  They are a lose cosmic ray away from all that coin being gone forever when they form a transaction and send all that change at once. Or some crazy glitch causes them to reuse a K value in a signing... private key is revealed... all that gone goes bye bye. etc.

The reference client has unit tests that should catch systemic failure, compiler bugs, etc— but if some crazy faulty hardware or radioactive whatsit makes you send change to an address you can't sign for... you're SOL.