Like sadeghi we did the climb in 2006 with Roy Safaris I would certainlty recommend Roy's agaiin -- they were great. We also did the Marangu route (my son was 14 at the time and i wanted the benefit of an easier hike). Since we went in early June, the sites were busy, but not crowded.
That being said, I agree with ajohn that the alternative routes would make for a better hike -- but I wasn't disappointed at all with what we did.