Mel,
Thanks for looking into this. My DD has used EPGY for math acceleration for 2 years, although once we hit Algebra I, the program wasn't suiting our needs (quirky CD-ROM lectures that were boring and confusing).
I think EPGY math K-7 is a very comprehensive program. I can't speak to the language arts or other programs. I would consider doing this for DS, but I'm not clear on a few things - are you saying "we" (i.e. this forum) would qualify essentially as a homeschool group? Is the fee for each family, or as a whole group? Either way, it is clearly a bargain. I want to say we paid $400 every 3 months for DD!
The SSA (technical support person) is a necessity. The program has some glitches at times, as well as some idiosyncracies to get over (e.g. inputting the answer sometimes takes some trial and error).
The difference between signing up as an individual and as a group seems to be the level of support. For K-7 math, we had an advisor at Stanford, but we never used her services - DH is an engineer, so he worked with DD. If we signed up as a group, each child would need his/her own supervising teacher. other than that, it looks like an interesting possibility.