It was perfect for us for our purposes at the time. DS needed new material, challenge, exciting community of amazing mathy kids, and a very clever instructor. Ideally, to get the most out of the class, I would suggest someone already have taken Algebra 1 and invest at least 5 hrs/wk time (outside class). Maybe not 7 consistently, but 5 probably--I would think 7 would be difficult since it's after school. Then maybe a little more when the crunch of turning in the Challenge Sets.
My DS11 just took Algebra 1 and I think it would be a class well-suited for him (if he were mathy) because it would build on what he's learned and go deeper/more complex. I will offer it to him in the fall, but I doubt it's something he would elect to do (though he always surprises me).