Trezor FAQ says
If you do not use a passphrase, your recovery seed is all that is needed to access your bitcoins.
If you do not use a passphrase, can the Trezor seed be used to recreate a hierarchical deterministic wallet?
Yes, Trezor uses the BIP0032 standard to derive your keys from the seed. That means you can use any BIP0032-compatible client for recovery, or you can even use them simultaneously (but be aware of the security implications - you don't want it to leak, otherwise it beats the whole Trezor purpose).
For example, Electrum works great with HD wallets, but I'm sure you can find other clients as well.
Sure. Yesterday MultiBitHD committed support for Trezor. I think MulitBitHD is still in Beta, but you could probably still try it out.
