DS8 enjoyed the MATHCOUNTS/AMC 8 Basics class. The live class is good to follow along in real time and answer questions quickly, which DS8 did reasonably. I would sit next to him and watch and observe how he responded to detect strengths and weaknesses, and maybe add explanations of my own, and I like to observe what the AoPS people do and see how they think. (And I paid for the class so I'm going to watch it too.)

There are 12-16 homework/challenge problems per week that are graded instantly just like Alcumus. (There wasn't human-graded written work.) He probably took longer than average because he was probably a little less prepared/experienced than the others, as he'd only taken prealgebra.

For AoPS courses I've been debating whether to use the class or just the book
http://giftedissues.davidsongifted.org/BB/ubbthreads.php/topics/197574/AoPS_Book_vs_Course.html
and I'm hoping DS8 will work through the book when there is one (but the contest preparation classes don't have a book).