I use it for my automated backend and I have to drop to a lower level command to force a tx when I have funds but they are unconfirmed and I need it to go out immediately. I actually wish sendtoaddress had a [minconf=1] option with a default of 1 that would allow finer control but it doesn't.
A couple of times I have resorted to doing a "getrawtransaction " then pasted the raw tx into
https://blockchain.info/pushtx (and that has actually worked).
I have done exactly the same, but that's just because people I send BTC to get nervous when the txID I give them doesn't appear on the network (well, blockchain.info). That's what led to this ... discovery.
As an aside, I've raised the issue here:
https://github.com/bitcoin/bitcoin/issues/3288