I planted the seeds on February 3rd, in Frey potting mix and put them on a heat mat under a 4 bulb shop light. Had sprouting in 3 days. One seedling didn't get past sprouting but the other 4 grew strongly. Now on March 14th, the strongest seedling has flower buds and the others look poised to follow. Impressive! I've had great success with the Multi-bloom zonal geraniums from seed as well. They aren't quite as precocious but this year's batch had 100% germination and they are lovely, sturdy little plants that will be blooming soon enough.
I was also very pleased with the prompt and thoughtful response I got from Customer Service when I asked what "treated seed" meant.