Having once been the General Manager of a local camera store chain, I have seen many DSLRs with dust (and other material) on the sensor. Mostly though, it was dust and sometimes hair, in the mirror chamber. A regular rocket blower will dislodge the particles and they will fall out if you hold the camera with the lens opening down. The same for sensor dust. For dust that does not come off (and is not stuck due to oil), there are some particle removers that will take them off. If there is oil on the sensor, then wet cleaning is needed.
Now, with all that said, I have seen more dust on full frame cameras (regardless of brand) than APS-C cameras (with the exception of an Olympus E3 - a real dust magnet).
So, for my use, I have a Delkin sensor cleaning kit that contains an optical viewer with light, a ionizing blower, cleaning swabs, and fluid. I have only had to use the wet cleaning on a Canon 5D. All the others came clean with either a rocket blower or the powered one in the kit.