Well I run at 40ppp. I prefer to not click as much, but just read. However, your initial statement is misleading. You neglect to mention "default" ppp. Your reasons for changing to 10ppp are valid and good ones, and the fact that I can change them as a registered user is great, but your question didn't say that, so I voted 20. For the reasons of guests and bandwidth, 10ppp is a better number.
If you change the question to "default" length, change my vote to 10
otherwise if the option was there I'd do 100 posts per page.
edit: haha! seems I'm not the only one confused about the default length thing. Best get a fixin'!