Read both Flashpoint #5 and Justice League #1 (Spoilers below).
With Flashpoint, it felt a bit anti-climatic. Overall I felt the Flashpoint main series was too rushed. It promised a lot of big stuff and I don't think it delivered. I do think the final issue at least got back to the series being about the Flash, whom I felt got lost a bit in the other books. There wasn't much payoff with the big battles either. To some extent, the megaweapon that took up so much discussion in the Aquaman/Wonder Woman books turned out to be a non-event. And it seemed that none of the characters, except Flash and Batman got any resolution. So many of those three-issue miniseries (with the be concluded tag) were left unfinished. Maybe these things will be taken up in later nuDCU books.
As for Justice League #1, I really liked the artwork. It took me back to Lee's X-Men #1. As for the story, like many others, I thought it was serviceable, but nothing special. I thought Hal came off as way too much of a jerk. Being a little cocky is fine, but he was an ass. I was surprised by that because it seems to me that Johns generally writes Batman as a jerk, but in JL #1, he came off as pretty regular. I liked the intro of Vic Stone and it will be nice to see his transformation handled within the pages of the book. The choice of Big Bad makes a lot of sense.
I can understand the criticism of the CBR reviewer. It would've been nice to see all of the Justice League in this book. Also since it was higher priced, a larger page count wouldn't have hurt and made the book feel as special as they were hyping it to be.