First off, I'd like to throw Bitlocker back in the ring and tell you that boot volume encryption is relatively unimportant for the threat model you propose, specifically untargeted data at rest.
Boot volume encryption/verification is designed to protect you against attackers who would replace your boot image with a one that contains a rootkit or keylogger. This threat model requires serious forethought and planning on the part of the attacker. He is likely targeting you or your company and he wants to do it steathily. Under this kind of threat, you really need the entire company to adopt an extremely high level of operational security. (Remember your security is only as strong as the weakest link in the chain.) Usually, this kind of paranoia is reserved for three letter agencies.
I should mention that Truecrypt doesn't protect against this threat either. At some point, there needs to be an unencrypted bootloader, which can be attacked. Hardware boot volume verification would verify that the bootloader has not been modified, which is what TPM tries to do.
Unless the encryption is implemented poorly (which in Truecrypt and Bitlocker is not) an attacker with access to your boot partition cannot attack your data partition without additional information (like your password).
On OS X, I've heard good things about PGP Whole Disk Encryption. I don't know if Truecrypt can handle Boot Camp (PGP WDE can), if you care about that at all. On Linux, I use dm-crypt + luks