TPM modules, Are they of any practical use?

My motherboard has a port for a TPM module. I looked them up, but there isn't much info on them.
I have Windows 7 Pro. Do you need the Ultimate version to use TPM? Do they slow the system down? Is the encryption worth while? Are they an improvement in internet security or a waste of time?
That is pretty much what I thought. I ran across some that were suggested by Amazon for around $15 (microsoft). I thought they would be more expensive. But it renewed my curiosity on the topic.

One website mentioned that they slow the system down. It also seemed that it needed bitlocker to work, which I don't have anyway.