Need to format brand new USB hard drive, or not?

I happen to use encrypted now because the hardware is sufficiently fast that you don't notice the on-the-fly encrypting and decrypting. It isn't that I have anything particularly sensitive on the drives; on the other hand, if someone broke into my house and stole my drives, I'd rather that they didn't have access to everything.

So, encryption is up to you. If you do encrypt, make sure you absolutely, positively do not forget the password!