i would pay for it. but as i understand it's up to the person if they want to subscribe or not. it's not a mandatory subscription.
as for paying $2.50/month... that's nothing! from all the money you've made/saved from HD, you should be happy. And to show that you are grateful for this service, I would pay. It's not much.
Maybe if they offered a lifetime subscription for like $60, i think i'd definitely pay for that!