The following are some reviews of the first volume of Ultimo in English, published by Viz. Follow the link to read teh entire review.

From Anime Vice:

From Anime News Network: http://www.animenewsnetwork.com/right-turn-only/2010-02-16

On one hand, it’s a typical boys’ action comic through and through, but the concept has potential. Chalk up a C+ for this one and see what happens next.

From ICv2: http://icv2.com/articles/news/16803.html

Like many manga, the creator has included levity at peculiar times, by American standards.  The title character Ultimo, while repeatedly described as a boy, is dressed in a very feminine tank top outfit throughout the story.  These are very minor issues in an interesting story.

From Manga.about.com: http://manga.about.com/od/vizmedia/gr/Ultimo1.htm

Despite these stylistic issues, the story was compelling enough that I can definitely recommend Ultimo to anyone who enjoys Shonen Jump manga or who likes shonen manga in general. It’s more than just the sum of its parts. Ultimo provides a solid reading experience with characters you want to know more about, in a situation you want to see resolved well.

From The Manga Critic: http://mangacritic.com/?p=3278

Given Ultimo’s pedigree, it should have been one of 2010’s must-read manga — a tangy, peanut-butter-and-wasabi pairing of superhero titan Stan Lee and cutting-edge manga-ka Hiroyuki Takei. Instead, Ultimo turned out to be more of a PB&J affair, competently executed but utterly forgettable. Takei, who’s credited with the script, relates the story at a brisk but comprehensible clip, introducing a large cast of characters that includes Yamato and friends in both their present-day and feudal incarnations.

Ultimo volume 1 was released February 2nd, 2010. It is currently being published in Shonen Jump by Viz in the USA.