And it is not as horrible as I thought it would be, after reading all the comments and reviews on the internet. In fact, it is enjoyable, if you take the story lightly, ignore the plot holes, and read through as fast as you can without stopping to think what exactly is going on. As far as I am concerned, Ultimatum is meant to set a new status quo to the Ultimate Marvel universe, and a fine job it did. Characters not needed? Kill them. No need for Ultimate X-Men? Murder Xavier and Magneto. And to make sure there really is no chance of reviving the series, kill off Cyclops as well.
And that is why Ultimatum is good. I do not have to follow and understand its plots much. It matters not to me how or why things happen that way. I know that Magneto screwed Earth, and then characters were dying everywhere. And voila! Status not quo. Instant ultimate universe “reboot” in several issues. One twelve-issued, universe-rebooting series is more than enough.