Poor choice, I just don't see him pulling it off but in the past choices initially thought of as poor worked out and were great (Heath Ledger as Joker). As of right now I just cannot see him pulling off Lex Luthor.
I'm not a fan of Eisenberg. And I really hope he won't play Lex like most of his roles. As for his look, I think bald would look good on him. As for his age, I like it that he's the same age as Cavill. Just like BaleBatman/LedgerJoker, it's interesting to have the main hero and villain to be around the same age. I know age didn't play out that huge in TDK but it was there. Joker wasn't a whole lot younger nor a whole lot older. And I like that Lex will be around Supes' age. Although, Eisenberg can easily fit for a younger version, he can make that convincing as well.
For the totality, I just hope Lex is a well written character. We haven't seen the definitive version of Lex Luthor on screen before (sorry Hackman/Spacey) and it's about them we get that. I think he's the best Superman villain and a very interesting character.
But I remain skeptical about Eisenberg as Lex until we get some concrete footage, unfortunately that's gonna take a while. Hopefully we'll hear Eisenberg himself about the casting soon, I'd be interested to hear what he has to say about it.