I sometimes get stuff growing on top when I don't have enough airflow, but mine was much more extensive, running around and down the side of the cup. I must have packed too tightly. Yuck.
Glad it works for some as the cost is great and you never run short. - Lisa

[QUOTE=pmcgrady;676718]I fill with MG potting soil, no mold issues just have to clean a bunch of sticks out of the mix.[/QUOTE]

To clarify, do you dense plant in seed starter and then repot into the paper pot with mg? - Lisa

I start all seeds in cell trays, then transplant (deeper) to paper cups, grow in paper till ready to transplant in ground.
I use MG potting soil in the cells and in the paper pots, when planting out I dig the hole, sprinkle a little Osmocoat, fill hole with ProMix, tear off newspaper/tape and plant the tomato in the ProMix. It works for me.