I've had a good think abut this one, as there are two considerations at play. Yes, I want to be first in the queue, but as my commute is all downhill except for one roundabout, then I will filter, or outright overtake wherever possible.
The chances of holding up a car driver for me isn't an issue (except when I shed a chain the other morning but that's a different matter!) On one roundabout the cycle lane splits the approach, so that you have a lane for traffic turning left, a cycle lane, and a lane for straight on/turning right. I'll therefore get to every set of traffic lights, every junction and two out of three roundabouts generally faster than the cars anyway.
On the last set of lights onto the ringroad I'll pretend there's an ASL and go to the head of the queue. I always make sure I get away as quickly as I can, and we turn right onto two lanes anyway, so I'm not holding anyone up.