The private keys of your trezor never go out from it, and you can always check in its screen the transaction parameters to see if they are correct or not.
I have not seen yet any trezor hack.
Boy wouldn't it suck to find out one day that the Trezor devices were simply using wifi to transmit the information on them?
There are so many suspicious infommerical-sounding posts for the Trezor all over the internet right now, I really wonder how many are legit.
In my opinion, you have to be a complete idiot to trust your money to any electronic device, provided by any 3rd party, for any reason whatsoever right now.
Paper wallets all the way.
-B-
Please read the docs first
http://doc.satoshilabs.com/trezor-user/securityphilosophy.html . Do not you think, if there will be any wi-fi integrated in the hardware someone will already find out? Do not you think if there will be some security issue, people like Andreas Antonopolous will be even bothered to mention Trezor device as a secure solution
http://www.reddit.com/r/Bitcoin/comments/2mz3q3/new_identity_of_andreas_m_antonopoulos_secure_and/ Yes, paper wallets are safe, but you still need to load private keys from paper using a trusted computer to send your coins to somebody else. Also if you do not understand, how change adresses work, you are most likely to loose your coins.