Well, this will be short, sweet and to the point.
Color me extremely disappointed in this book. For all the flaws that Ultimates 1 and 2 had (and most of those being issues of scheduling), they had an energy and an excitement to them that drew the readers in. Well, they drew me in at least.
This first issue was disjointed, jarring and poorly explained and executed. The story begins in media res which can be hackneyed in the wrong hands, and in this case Jeph Loeb's hands are the wrong ones. Most of the characters are cyphers, with seemingly little progression from the two previous series.
There just isn't a lot there to sell the book past this first issue. The only real comparison that I can make is to the Heroes Reborn run on Avengers (which Loeb was involved with as well). The comparision, however, doesn't help Ultimates 3.
Unless this book picks up, and quickly, I don't see my following it.