I have only had one sensor clean about 2 yrs after I bought my canon 400D. It was pretty bad but got a 100% clean result, well at least for a couple of days :-). I was told by the guy that did the clean that canon tend to over lubricate new camera's (which is a good thing) which can lead to difficult to clean sensors if the lubricant gets on the sensor which it had in my case.
Once the sensor was cleaned the Canon sensor cleaning design seemed to do its job pretty well. I am pretty #### about how I change my lens but dust is un-avoidable and sometimes I think we get a bit to carried away about it (my opinion only).

My 50D is about as bad as your sensor after the clean and to be honest, I would be pretty un happy with that result. Will take it into Gavin for a clean soon. I think the first clean is important as it removes any production line impurities that may have found there way to the sensor but I also must say (and not sure if you have a canon) that I find the built in sensor cleaner seems to do a pretty good job at keeping the sensor relatively clean.

The other thing I do is ensure my lens element covers are as dust free as possible as with the end elements also to avoid dust build up on the element end of the lens finding it way into the camera and I do clean them on a regular basis. Works for me anyhow.

Cheers,

Mike