I got a soil block maker at the beginning of seed-starting season(which is February around here), hoping to get the convenience of peat pellets without the added expense. So far I've had mixed results.
Most of my seeds germinated just fine in the soil blocks, but shortly after gaining their first or second set of true leaves they seem to have stopped growing. These were planted sometime in March - I'd think the plants would be a lot bigger by now!
I've heard that if you pack your soil blocker too tightly the roots have trouble penetrating. My first few blocks were loose enough that I had trouble moving them without crumbling, so I packed the next set more firmly. There's no way for me to know what's too tight or too loose except trial and error. It's also possible I might not have watered them enough - or I might have watered them too much! I hate it when diametrically opposed actions result in the exact same symptoms! I've tried potting some of them up and attempting to loosen the soil a little, but so far it doesn't seem to have made much difference.
So far the broccoli I started at the end of February hasn't gone much past this stage here. I planted them out in hopes that being in the ground would encourage them - I'll let you know if it works.
My sage, on the other hand, was planted in a peat pellet, and is going gangbusters, along with several other varieties of herbs.
I'm not all that upset, because I knew that soil blockers had a bit of a learning curve. At the most I'm annoyed at the prospect of not having some of my longer-growing veggies (namely broccoli and eggplant) this year. I'm probably not going to have time to try and start the eggplants again if these fail to thrive, but I can start more broccoli seedlings for a fall planting. I think next year I'll stick to the peat pellets for these, and experiment with the soil blocks for plants that grow faster, so that I have time to try again if I don't get it right the first time.