I don't like the fact that you have to log in to some interface to get your coins out of the wallet. What happens if I don't have internet? I don't want to depend on some webpage to get my funds out.
well if you don't have internet connection you won't be able to send that btc anywhere anyway
you don't have to use mytrezor frontend http://doc.satoshilabs.com/trezor-apps/index.html
anyway, now i have one of those
i don't trust it with whatever left from my coins in 100%, but then again i don't trust ANY storage with all my coins
paper wallet is great, but you have to have a lot of knowledge to use it safe, and there is that point that you need to move your private key to some electronic device to spend (i would like to see private key import in trezor v2)
any electronic device, including trezor can be hacked in one way or another, it can be pure firmware\software vulnerability, it can be hardware based software attack https://www.cl.cam.ac.uk/~sps32/mcu_lock.html or something else, it is just a matter of how bad someone want it hacked, how much skills and resources he has and how much your devices are exposed - there is almost always some 0day available for your OS, browser, wallet, IM, etc., and if is not there right now it will be soon enough
but with reasonable precautions you can be safe enough
what i fear most is that the initial key isn't random enough (but that is also the case with any private key generation let it be core, some offline java generators etc.) and if that kind of problem is discovered at any point in the future it allows to steal your coins no matter how far you went to protect your own copy of a key
other than that i trust trezor enough to have some coins there for every month use