They haven't interacted much, so Itachi is pretty neutral on him. Talking foxes kinda ping him for demon beasts, but Tails is about as far from that as you can get, so he treats him kind of like Skyler--some sort of sentient beast person.

As to personality Itachi doesn't have much opinion on him, he seems nice, and helpful, and Itachi therefor sort of lumps him in with a lot of the people he deems "good guys."