I was thinking about buying a Trezor, but what's the point when you need to be online and log in into that mytrezor site? what if that site ever goes online? it's pretty dumb to be honest, we wouldn't need any connection to the internet to use it, that doesn't sound very cold storage.
You can use the Trezor with other wallet software:
http://doc.satoshilabs.com/trezor-faq/overview.html#which-wallets-are-compatible-with-trezor-hardwareNo need to use the mytrezor site.
Are you program developer ? you can't know it's100% trust.
the seed show up on the trezor thats correct but it also synchronized with their site
Not it's not. Do you have any proof of this?