anotherbrian succintly summed it up. TPM by itself doesn't buy you anything without a software stack on top of it that weaves the keys for OS' encryption support back into the TPM. Vista will do that through the BitLocker program.

AFAIK, some other laptop vendors have proprietary solutions. I haven't seen any commercial "user" level applications that use TPM yet. Maybe I didn't look hard enough.

Most of the TPM/TSS stuff is still at the level of device drivers that software people get excited about. Nothing an end-user can leverage simply.