I'm just kind of surprised that Obito's eyes turned out to be so powerful.
I mean, Obito was a loser (from the larger perspective of the Uchiha clan as a whole), and he had only managed to awaken the most basic level of the sharingan's abilities at the battle of Kannabi Bridge (at a late age, for an Uchiha-- compared to Sasuke/Itachi).
Considering that Sasuke/Itachi, geniuses of the Uchiha clan, are only able to use their Mangekyo for what seem to be the most basic/generic Mangekyo Sharingan abilities (Amaterasu, Tsukuyomi, Susanoo), it's bizarre to think that a "dud" like Obito had eyes that unlocked such an incredible level of Space-Time Ninjutsu. It's hard to believe that Tobi (if he is not Obito), would know to steal the eyes of a typical Uchiha brat who, until the battle at the bridge, didn't even have access to the Sharingan. In the midst of a massive scale world war in which the Uchiha also participated (and presumably faced casualties in), how would one man know to follow around a "3rd rate" brat that didn't even have an awakened Sharingan yet?
What's even more strange is that despite the uniqueness and power of Obito's space-time jutsu, Tobi is able to utilize the power so freely, and at will. Just think about the fact that Kakashi is only able to use Kamui (a much more limited technique) a few times a day. Similarly, Shisui's unique hypnosis jutsu would force his mangekyo to close for years on end.
Of course, we don't know exactly how the chakra consumption of the various sharigan techniques work on their various users, but it's safe to say that Tobi is pretty incredible to be able to use Obito's eye to this extent-- even if he is Obito (the one who you'd think would have the best compatibility with the eye, considering they're his eyes), it's pretty unlikely for any Uchiha to be able to abuse the Sharingan's power so freely, let alone a unique Sharingan ability. Considering how he was able able to control the Ninetales (possibly with just a normal Sharingan?), and utilize the Rinnengan (and likely Tsukuyomi as well considering his goal), Tobi must have a body far superior in stamina and compatibility with the Sharingan than any Uchiha we have seen so far (besides Madara).
Finally, and this is just fanboyism, consider that Tuskuyomi is a eye technique born of one eye, and Amaterasu the other. When both eyes work together, Susanoo can be activated. Similarly, Kakashi and Tobi seem unable to use each other's techniques, because they only have one side of the set each. If the two eyes were brought back together, I wonder what kind of insane space-time jutsu would be born.