It would be nice if accuracy could be traded off for time, so that instead of getting a more accurate lock, we're getting a the old accuracy but quicker.
For me the biggest limitation of GPS is that it can take > 1 min to get a lock on a regular basis. I know this is hardware and software dependent ... but it's still common for it to be at least 20 seconds even on the best hardware, I think. Apart from making apps that rely on GPS awkward ("please wait an indeterminate amount of time while we find your location") it also means much greater power use because the GPS has to be active for longer (GPS seems to be something that noticeably uses a lot of power in my Nexus One).