If you have cost effective mobile web access, I personally believe the way to go is a mobile web based agregator. Two good ones are Feedalot and Bloglines Mobile. I wrote about them on my blog in this article;
http://wapreview.com/blog/?p=37 with a couple of updates in
http://wapreview.com/blog/?p=43 and
http://wapreview.com/blog/?p=60. I keep up with 60+ feeds on a mobile phone with a smaller screen than most PDA's during my 2 hour (round trip) rail commute using Bloglines Mobile and Feedalot. The nice thing about both of these agregators is that they have a web version and a mobile version which stay in sync with each other in terms of what feeds you are subscribed too and what items you have and haven't read.