That's how most non-plug-in Toyota hybrids work. They have a NiMH battery at 288 volts (nominal) and to run the motor at higher voltage there is a voltage doubler at the input to the inverter.
In Toyotas, far as I've seen, the voltage doubler is only used when it's called for. Otherwise it runs at the standard pack voltage. And, the voltage doublers in, for example, the Priuses, are considerably limited in current they can handle compared to the rest of the inverter.
Some guys have thought about using them to gain higher speed, and changed plans when they saw the lacking performance.
Not sure if everyone would feel the same way, most people seem to just want to be able to go reasonably faster, they're not looking for performance.
IIRC Johannes has got field weakening working, but it's a bit buggy and the openinverter community has been going over it with him with what works, but aren't sure exactly why it works or if that's a best practice. It's a software thing.