I've heard a lot about this story, and I know this is an awful sin for a big nerd like me, but I'd never read the original Proteus story until last week. I've read lots of follow-ups and adaptations (including the X-Men cartoon and the great long-running storyline in Exiles) but I've somehow avoided a lot of the X-Men issues between 100 and 200.
This story holds up nicely, even if it is a bit short. There is a ton of Chris Claremont's signature mind-control (Jean Grey is getting set up for her Dark Phoenix storyline with Mastermind) and that was a little tiresome. However, I LOVED seeing Cyclops as the man with the plan in these old issues. Proteus does a heck of a job taking out Nightcrawler, Storm, and Wolverine, and Cyclops is justifiably concerned that the three heroes have lost some confidence after their defeat. So he straight up starts a fight and starts blasting them around to make sure they've still got their heads in the game. He's a bit of a jerk, but that's one tough leader!
I expected a bit more from Colossus during the storyline, since he's so important to the resolution. It also is interesting that Banshee, Moira's current beau, has no powers through this whole story. Banshee is one of those characters I never appreciated when he was alive, and I bet it would have been neat seeing him do more during this bit of X-history.
John Byrne's art is fantastic, of course. No one draws these characters better. I do have to laugh at his skin-tight outfit for Moira, she's one slinky scientist.
The back-up material in this is nothing to write home about, but it fills out the hardcover with some more material, so I'm not going to complain too much.