I still use my Palm TX, mainly because I can't get my Sony reader back from my mother. (Maybe I need to buy another one.) However the TX is much more portable & therefore it is easier to follow an old military habit of taking advantage of any spare minute or a dozen to read since it is always with me. Also when my wife wants company when she goes to the horse barn, I have a back light to use while I wait.
Bottom line - I like them both.
I wish there was an easy way to sync their bookmarks.