We are very impressed with the Potting Blocks method so far. We started our first seedlings March 5th, and many are up or crooking their tiny stems. Keeping the tiny cubes warm has been relatively easy, as has been keeping them wet (thanks to the misting apparatus).
Here is one of the seedling trays yesterday, one week after starting:
Perhaps today we are making a tray of little ones just to start spinach in. Spinach is known for its sparse germination when direct seeded in uneven weather. I look forward to trying the tray of 300 cubes. It may be more work at first, but once my seeds are all warmly up, I can transfer them to a perfect row outside with no 'blank' spots!