Wow! Now this is how you do a crossover event! This follows 4 different series with different writers and artists, and yet everything felt entirely cohesive as if it was just one series by one writer and artist. This is done at the cost of each series not feeling wholly like the series would normally feel; for example X-Factor had to advance X-Men's plot, and Uncanny X-Men had to advance New X-Men's plot, and so on. The series all got melded together, but this is for the best. There were generally 5 or 6 different plot threads being advanced on each issue. I used the word "cost" earlier, but honestly this is exactly why this crossover works so well--because it feels like one cohesive series. The writers matched up their writing styles well, and the artists' styles were similar enough that it never felt jarring jumping between 4 different ones. The only reason I used the word "cost" earlier is because if someone were reading any of the 4 series by itself, reading only the issues from said series would feel completely jarring, and skipping them even more jarring. So the only option is to read the whole crossover event, which might still be a bit confusing if not reading the other series involved. Everything is explained well, so one could easily read this standalone, but a lot of setup was done in each of the series involved beforehand, so the full impact would be lost. Still, this is a very minor concern as the event is completely worth the time.
The plot itself starts out fairly simple: various factions searching for a baby. Eventually, twists are introduced adding depth to the plot. By the end, things come together smoothly. Having read X-Men, Uncanny X-Men, X-Factor, and a volume of New X-Men, I felt like I got a lot more out of this crossover, as plot threads that had been sown way back in those series get used or resolved here beautifully. It also helps being familiar with all these characters, their motivations, and their current states.
I think every single writer wrote very well. I am a huge fan of all of them individually in their series and other works. I feel they might have been a bit more stiff than usual since they needed to make sure everything was going according to plan in terms of plot elements and pacing, but their seamless collaboration more than made up for that.
Every single artist knocked it out of the park too. Even Scot Eaton and Humberto Ramos, who can be a bit hit or miss for me, were on their best game. And Silvestri, Tan, and Bacchalo were incredible as usual. It also helped that D'Armata colored two of the series along with the one-shot, and that Delgado and Reber have similar coloring styles. Every series flowed well from one to the other.
All in all, I would give this a hearty 9/10. Solid writing, good art, lots of action, lots of status quo developments, and even a bit of character development here and there. Due to the fast paced nature of the event some parts weren't as fleshed out as I'd like, but it's understandable. I look forward to reading the series spanning out of this next.