Apparently the on-board cameras are finally going HD next year! Hopefully the cameras will be of decent quality aside from the resolution though, and not like the ones they use for Le Mans/WEC, which suck at capturing light changes/motion realistically, and put out images that resemble those of a mobile phone camera.
To be honest, the HD probably won't make much of a difference on BBC HD, as the bitrate is relatively low and they appear to use some aggressive noise-reduction (presumably to improve the compression), which destroys much of the extra detail of the HD feed. The difference will be massive on Sky, though.
I don't have any way of measuring the bitrate myself, but a few people have tested it (presumably with a tuner, a smart card reader and some kind of illegal VideoGuard emulator on their computer) and have found that Sky typically puts out significantly higher average bitrate (earlier in the year, at least).
You can see the difference for yourself by taking a screenshot of each channel at roughly the same time and zooming in on bits of the FOM graphics (especially the F1/LG logos). Even on a TV at normal viewing distance, it's still quite obvious when you try to distinguish all of the lines on the '1' in the F1 logo.
Apparently BBC turned up the bandwidth around the time of either Wimbledon or the Olympics; I've got no idea if it's remained that way, but regardless, I'm pretty sure they're still abusing the noise-reduction, as the FOM graphics still look clearer on Sky.