I don't know about the rest of posters on this board, but I am getting really tired of all these spin off series coming out of JSA when the main title is so conveluted. I have intentionally avoided Power Girl and Magog and nothing I am reading on the boards is convencing me that was a bad move. I will buy the 80 page special coming out this month since it looks like an extention of the main title. I am debating about the new All Stars comic. DC is going to have to give me a really good reason to add this to my pull. I also expect the main boo to do some shoring up and start having decent stories after the clean house or it's days in my pull may be numbered too. I love the Justice Society and I love Golden Age and legacy characters but this title is really floundering at the moment.
You should buy at least an issue or two to give them a try. Magog's not too interesting to me, but I've enjoyed some of the Power Girl issues. The latter series is uneven, but overall, I'd give it a B.
The new All-Stars issue that just came out today was above average. The pacing could have been better, but it was an entertaining read. Stargirl and Power Girl have a nice quiet moment together between the action sequences.