http://www.leevalley.com/en/garden/page.aspx?p=69004&cat=2%2C47236
A little video on using these, has anyone used these?? If so, did you like them, was it work the money? I really like the idea of them, but I don’t like the idea of needing to buy the soil making itself, as I typically use everything from the farm itself but having said that, there are some things that I do start in potting soil and I would raither make it myself and control how it was done.. I have alot of pots so that is not a issue but its more about limited space in my greenhouses, and that this could work to really max out that space..
how many years would you need to use them to get your return on them?
http://www.youtube.com/watch?NR=1&v=k2m8-hfhtDU&feature=endscreen
Just another Day on the Farm 
Interesting gagget but I would not use one. They look like they would take up a lot of time but then again I don’t have a space issue.
How big is your greenhouse space?
When organized it is the whole top floor of my house so about 20 x 12 but my yard is small so I don’t have the same requirements as you.
I’m not sure either. When reading Coleman’s book, I was interested but then I mostly do things in flats or in situ or I have precious seed which I use in a baggie so tend not to. However, maybe I’d love them if I tried. I’m also suspicious of product though ones that last awhile and are genuinely time saving like my ‘suzy’ the apple peeler, I love.
Hey FG, Lee Valley Tools sell (design and manufacture) excellent quality products: woodworking and garden tools, a massive array of hardware (for cabinet making and just about anything else you can think of) have a great series of reprinted, antique books, stand behind everything they sell – no exception – and actually encourage customer input on product improvement. I’ve been a Lee Valley customer for somewhere around 30 years and often wondered how these work, so thanks for the link.
As to return on your investment? How many seedlings do you currently have room for in your greenhouse and how many more starts could you do using this system? What are your current success rates for seedling germination and transplant survival? Could these be improved with a lighter planting mix? Have you saved 50$ yet, or how long would it take? And don’t forget to add your time (spent with this method & saved by not actually using/reusing pots) into these calculations; )
Found this article as well: http://pacificpermaculture.ca/www/articles/87-soil-blocks-for-sustainability.html
Going to take these questions and work them into a blog post..