When I first started reading ebooks I insisted on autoscrolling which is why I went with iSilo. I converted sooooo many books from say LIT into iSilo format specifically because I wanted to use the autoscroll. Since then I've come to prefer simply paging the book myself. I've found I can comfortably hold it in one hand and press the downward motion on the main button of my iPaq (what is WITH the crazy capitlization of these products by the way!
So basically I'm just trying to speed up how quickly I read without missing anything. I can't skip around or skim when reading fiction because I feel like I'll miss something important. And of course if it's a particularly well written book (as opposed to something pulpy which almost begs to be breezed through) I want to savor the words.
Oh well. It's an interesting thought. I don't know if traditional speed reading techniques really work well on a pda. I did read somewhere that simply trying to read the words faster and not stumble and re-read is beneficial and may even 'train' your eye muscles. Not sure if that's true or not. I do know that our brains can process the information faster than most of us can read.