I am interested in reading A4 pdfs on small readers as well. In my experience with the 6", the "new" reflow firmware is actually fairly workable for this purpose - provided there are no images or tables to be dealt with. If there are tables in the page, the device will only display the page at the smallest setting, rendering it unreadable.
It seems to me the answer to this is to allow the user to choose either reflow or true zoom and pan as appropriate for the content. This video on the Sony PRS-600 suggests it is able to do this.
http://www.youtube.com/watch?v=oKpl4wiG-Bs
As much as I'd rather support Astak, after seeing this, I canceled my Pocket Pro order, as I believe my particular needs will be better served by the Sony device.