In bitcoin it's bad to reuse addresses (less security, as public key has already been revealed), how about ethereum? Is the public key revealed when the first transaction (first nonce) is used?
As long as your private key is safe you are okay in both bitcoin and ethereum, bitcoin allowed multiple adress for two reasons
- to keep personal and business transactions separate for example
- privacy, all transactions on the blockchain are public so someone can more easily follow you, having multiple adress can help with that, check this link is you want to increase your privacy on ethereum How to increase my privacy on Ether accounts?
and yes your ethereum adresses are hashes of public keys, so the actual public key will be revealed once you sign something with the keys