Endless page scrolling I would avoid.

In IE (majority of my visitors) - when you click on the scrollbar and drag it to the bottom, new content appears. Once releasing the button from the scrollbar - it jumps. Not going to in depth detail about it.

My suggestion - have a div appear at the bottom of the page (footer) and on window scroll or resize event check to see if the footer is visible to the screen. Then load fresh content.

I'd say forget the traditional scroll down technique. I've seen some sites that load content asynchronously in a horizontal manner and that feels brilliant. It's like you are panning a camera almost. Further, if you add mouse gestures to start the movement when the user's mouse is near the edges of the screen, it feels seamless.

I would implement an easy to work with/smooth endless page scrolling technique. You can find a good demo here, but make sure you select the "View Results" button to see it in action.

This techinque I outlined above utilizes a mixture of Ruby on Rails and Prototype.