I took machine learning the first time it was offered, and took about half of the PGM class before personal commitments won out temporarily (it was quite demanding, 10-15 hours per week). I re-signed up for PGM so I can give it another go this fall. Quality was really fantastic. Some people complained that ML was not as hard as the Stanford class, but I probably wasn't expecting quite that level in a free, online class, so expectations on my end were more reasonable.