Another of Chris's blatant rip-offs, it is a copy of "Super Sonic". Super Sonic is the result of Sonic collecting all seven Chaos Emeralds, which itself is inspired by the Super Saiyan transformation from Dragon Ball Z. It should also be noted that Ultra Sonichu is basically a recolor of Chris's very first failure Bionic the Hedgehog.
Sonichu #10 has shown that Ultra Sonichu has a plethora of super powers. Besides being able to fly, like Super Sonic, he also has Messianic powers as well. He is shown using his presence to revive Zelina Rosechu from her eternal slumber (and apparently to accidentally free Clawdorf in the process), and he uses a power called "Chaotic Remedy" to cure Asperchu and his versions of Sonichu and friends from all their maladies, such as personality.
So far there doesn't seem to be any specific time limit on Sonichu's ability to remain in his Ultra form, unlike Sonic's Super form, where his only weakness is the fact that his form eventually runs out. After doing everything he needed to do (which included curing every single Jerkop he and his friends haven't managed to murder of their brainwashing) Sonichu just kind of... stops being Ultra.
Ultra Sonichu evolves from Sonichu. Metonic also evolves from Sonichu. It has already been shown in the comic that Sonichu will eventually evolve into Metonic, so technically Sonichu will never be able to evolve into Ultra Sonichu... but he found a way. He seems to be a mega evolution now.
Star sign confusion
After evolution, Ultra Sonichu's star sign changes from Pisces to Aries. How this is possible is still a mystery. A theory is that Blake is the one to actually assume this form, since he is an Aries, much like Ultra Sonichu, and is supposed to have all the abilities Sonichu possesses. That would be an interesting plot twist to give Blake the role as the actual hero; however, considering Chris's writing ability, this is probably just a coincidence.