Can I ask what specifically he called? Was it that the seeds eventually would germinate? Was it taking a long time? Either way, glad they are sprouting for you!
I'm sold on the Rapid Rooters. I don't know if you saw this in my 2013 Glog, but for my 2013 grow I did a little experiment. I sowed seeds of each variety I planned to grow both in starter mix and in Rapid Rooters. The results were interesting. Of the cells that did pop (90+%), about 60% sprouted first in the Rooters, about 20% first in starter mix, and 20% about equal. Some popped only in one or the other. This was good enough for me to decide to go exclusively with Rooters for subsequent sowings. If some varieties don't pop in the Rooters, then I will make cells with starter mix to try to germ those. Of note, I had put four to six seeds into each Rooter and into each soil cell. This way I had a higher success per cell and could choose the dominant seedling, culling the others.
A few observations I noted about the Rooters relative to soil. One is that the seedlings initially did not seem to grow as quickly in the Rooters relative to soil and many turned yellow very young. This was corrected by watering them once with 1/2 strength Fox Farms Grow Big (6-4-4 with micronuts) once I noticed the yellowing. After that, they greened up and began growing at the same rate as those in soil. Another is that the Rooters seemed more succeptible to mold, even though the cells were not soaking wet. It seemed to come from the seed coat, not the Rooter itself, and occurred despite pre-soaking the seeds in H2O2/chamommile tea dilution. Nothing I tried killed the mold once it was there. (H2O2, Copper soap, Daconil). It also did not affect every cell (in fact, only a minority of cells). On a subsequent round of sowings, I pre-treated the seeds with a 10% dilution of bleach for 10 minutes, followed by soaking in just plain tap water. None of these seeds got hit with mold, which had proven to be deadly to the seeds/sprouts on the previous germination attempt, and the bleach did not seem to harm the embryo, at all. Of note, there were two types of mold I had develop. There was a white mold, which seemed to be harmless to the seed/seedling, and a black mold which seemed to be deadly. I also had noted more helmet-heads in the Rapid Rooters relative to soil, but not as many as I expected. I think multiple seeds per cell helped with this.
It's also cool to be able to look directly at the seeds and see when a rootlet emerges, as opposed to wondering what is happening down in the soil.
Hope this helps!