PDF may be OK, but IMHO PDF can be the worst, depending on the type of PDF. General fiction is usually OK, but technical books and magazines can be a problem. Documents with collumns and charts are usually hard to read on the small screen and don't reflow well.
Some prefer LRF because it will display justified on the PRS-600 and ePub does not. However, if I was going to go to all the work of converting from PDF to another format, I'd go to ePub. Time is running out for the LRF format. It has been dropped by Sony. The future is with ePub (until something better comes along).
Last edited by MSJim; 07-01-2010 at 12:14 AM.