Not enough to go on regarding his performance, acting wise. Just a few hand gestures and some movement. I've never been too worried about his ability to act the role, there are only a couple people I would have chosen for the Joker over Leto (My #1 choice, Daniel Day Lewis, would never even consider doing a CBM unfortunately). The voice Leto was teasing at his concerts would be phenomenal for the Joker, if that is his Joker voice it's basically perfect. Then it just boils down to how well the character is written, as good as Ledger was, I still think the biggest reason why I enjoyed his performance is because of how excellent the dialogue was. Hopefully we'll get a similar quality of dialogue for this Joker. If it is, I think Leto will give a very good performance.
As for how he looks... Sigh... I don't think I could hate it more. The only thing I like about it is his eyes. The blackened paint looks good and makes his eyes menacing. The tattoo's, the grill, the lack of eyebrows, the bright neon green hair, the clothes, the jewelry all look terrible to me. You could remove the tattoo's completely and I still wouldn't like it. I actually kind of like the idea of The Joker having some tattoo's (not on his face though) but the tattoo's they chose are just stupid. He looks like the lead singer of a Goth band, dressed in one of Leto's Red Carpet suits from his personal collection. I guess this is the down side of Ledger being so great, that they try to make the next version so different to distance themselves from his performance that they over do it and fail miserably. I can't believe that Ayer and the costume designers actually sat down, went over designs and picked this as the best one. I'm glad we'll probably never get to see the ones they discarded if this is the best they could come up with. It's awful.
It's disappointing because no one wants to see the Joker more than me. Over the last few years there were tons of people saying that it was "too soon" to do the Joker again because of Ledger's performance and I was the first person to call BS. They could have the Joker appear in every Batman related movie from now until the end of time and I would never get sick of the Joker character. To me he is by far the best villain of All-Time, there is no villain like him or as exciting as him. But this is definitely, by far, the worst visual character design for the Joker I've ever seen.