Ultimates is a book that caters speciically to the hardcore cosmic niche of the fan base. And given that we got a new multiverse with brand new rules, the timing of it was probably good. I don't agree it's exactly a Galactus solo... but I do think the book really isn't character driven so much as it's plot driven. He's essentially world building (or rather multiverse building) and re-establishing the rules and the shape of the new multiverse. And that's something I'm sure plenty of readers don't really give a crap about. But to the hardcore cosmic guys which this book is catering too, it's like crack.
Ultimates isn't for everyone. And I think by THIS point at least, most should have a clear understanding of what sort of book is it and what it's trying to accomplish. I won't have a HUGE audence, but I think from this point on it'll have a stable loyal one.