same thing goes through my mind. on the one hand he has at least one ems, so he's able to cast tsukuyomi and his ems-jutsu. possible that he has the second eye, so he's able to use susano'o, amaterasu and maybe even more ms-attacks. he sees through every attack, can instantly teleport or send his body into another dimension and warp his enemies away, so you will never fight him with superior number, nor is anything fast enough to hit him so far.
on the other hand, he has just one arm, and declared (and itachi confirmed it) that he 's just a former shell of himself. we havent seen any offensive jutsu by him so far.
therefore i'd say yes, he is strong, but i cant say weather he's strong enough to beat sasuke or naruto after his next powerup.