Perry makes some great points on cleaning.
All the bigger labs which include Fotokem (and former labs like Deluxe and Technicolor) always use ultrasonic cleaning as a common practice after film assembly. Although film right off a processing machine is relatively clean, the assembly (or prep) of film usually leaves behind some residue, dust, etc. Ultrasonic cleaning is the best and final step before the film is handed off to be scanned or printed.
As Perry mentions, ultrasonic cleaning is superior in that it can remove embedded particles, and other stubborn residue that alcohol cleaning might miss. This is because the film is fully submerged in more aggressive, warm solvent with ultrasonic agitation. Alcohol cleaning is usually used at scanning facilities for basic light duty cleaning due to lower operating cost, less regulation and health concerns which require special handling.
As far as we are concerned, there is no heath risk to us either way when we get the film back. So, I always ask for prep and ultrasonic cleaning with the labs I deal with. I believe there is an ultrasonic demonstration video at the bottom of Spectra's lab page in case anyone wishes to see how it works.