Afraid I must post a longer review (and a somewhat more critical one) in response.

First, I must admit this is most of my exposure to UF, but I quickly grasped it was a Fusion Fic of a lot of different properties as opposed to a standard megacrossover, and for the most part, it works well, and on the good side of the ledger, using Revolutionary Girl Utena as the core of this mega-arc was a good call on Gryphon's part, and as a fan of RGU, he consistently treated the canon of that show with absolute respect, modifying it only to the degree needed to make it share a universe with Magic Knight Rayearth (which I felt was fused slightly badly but otherwise worked) and his own Mega-Canon, which is an expanded version of the Ah My Goddess canon on a multidimensional scale, and the way they all work is actually rather ingenious.

On the somewhat less impressive but still decent side of the ledger is how several mecha anime were added to the plot. In this, Gryphon clearly invoked For Want of a Nail or In Spite of a Nail or even just cherrypicked what he liked and tossed out the rest, and while that rather annoys me (in some cases he tossed out all but the title robot and few key concepts and kept everything else), he did a great job adding Big O in an altered form as well as Gao Gai Gar. Gunbuster was also heavily modified (Noriko is in another dimension post-Gunbuster canon), but added quite well. I also have to admire how he said "screw it" and included the most badass Zaku II and had it plausibly win against the Shining Gundam in what had to be a rather amusing/awesome mix of Gundam canon which was so good the weak excuse tying it all to the larger plot didn't really bother me.

The bad side of the coin is Getter Robo, which keeps the concept of Getter Rays and the Robot and throws out the rest, and while it does get to do some badass stuff (with an RGU character doing Crazy Awesome stuff that would make Hayato Jin's jaw drop as the pilot), Gryphon flatly admitted he called it's second form (based on Getter Robo G) The Getter Ryger instead of Liger (despite being made aware of the correct spelling per series Theme Naming) and refuses to change it to this day, a fact that still makes my inner Getter fanboy's eye twitch on occasion.

The sci-fi aspect of the world mostly works, with Babylon 5 and Star Trek being fused together with some Star Wars thrown in, and while the latter is expertly done so as not to conflict with anything, B5 and ST make an uneven mix, especially since the Psi Corps from B5 are recurring villains, Earth Alliance is in a similar role, yet we still have the reasonably honorable characters of ST and the Federation around at the same time, which is hard to reconcile, and at times it felt like Gryphon wanted to have his cake and eat it too, glossing over canon issues and basically hoping the audience wouldn't care too much. Still manages to work somehow, but very badly at times.

The series also features a lot of lesser crossovers, like Halo and Giant Robo (which downplays the mecha aspect severely in favor of keeping the villains the central focus) that all manages to work reasonably well.

The original characters all tend to work quite well without being Mary Sues or overshadowing the canon imports most of the time, but the series tends to be way too hero friendly at times, with Gryphon having to rather transparently manufacture crises at times (to the point you can mark the exact point he does so) just to give our heroes some antagonists. Gryphon himself is a Self-Insert, but he manages not to make himself too overpowered, even handing his SI a large amount of conflict and angst towards the end of SotS that felt genuine.

That, however, brings me to the worst aspect of SotS, and I daresay the elements that at time drag the entire story down into "screw you, Gryphon, I don't care anymore" territory.

The man is a slave to his Author Appeal, namely whatever series happens to catch his fancy at the time and his musical tastes. The first is blessedly an admitted problem, and his obsession with Legend of Korra almost threw the entire mega-arc onto a massive derail until he rewrote things severely, but the second is at best gratuitous at times and at worst, outright masturbation.

To wit, when his original characters enjoy Gryphon's music, it's vaguely plausible. When canon import characters do it, it starts wearing thin my suspension of disbelief but is acceptable in limited doses. When he stops entire stories dead in their tracks to indulge his personal tastes and uses the majority of the cast to pimp his musical likes, I have to admit not only did I scroll ahead of a lot of those scenes (which had no plot relevance most of the time), I was more than a little nauseated at having to read the equivalent of watching Gryphon masturbate right in front of me, and while I apologize if that sounds harsh, I felt it was the weakest aspect of the entire work and it could have been trimmed or excised in many places without diminishing the rest of the work in the slightest.

That aside, the entire work (pre-Legend of Korra derail, now rewritten) was quite excellent on the whole, and I too give it a recommendation, albeit with the reservations outlined above.