HD Service Worth it?

[ApeAttack]

I'm going to get Direct TV and I can get HD service for another ~$10 per month (I already own an HD-ready TV). I am getting the HD receiver for free as part of a promotional offer.

At Best Buy, Fry's, etc... they compare HD with 'regular' TV and I can definitely see the difference. However, I don't know if I would be missing the improved quality with only 'regular' TV.

For those who get HD service, has it been worth it for you? Is it worth ~$120 per year? When you go to a friend's house and see 'regular' TV, does it look like crap?