I have ridden with four panniers for 2 touring seasons now and cycled camp from home in England to Santiago de Compostela in 2004 and then down and up the Danube in 2005. My velo was a Dawes Discovery 501 ( modified---- Velocepanther1). Front panniers are fairly essential for a good balanced ride but you know they are there when you are cycling into a head wind all day!
For this years tour ( starting 20 May) I have a new Velocepanther Mk2 because VP1 was stolen at the beginning of december last. It is another hybrid a Dawes Discovery 601 -- modified a bit but this year I have discarded the panniers all together and I am now towing a BoB Yak trailer instead.

I have attached 2 pics of my set up last year ( if they appear? not used to this site yet - and I don't understand how it works yet)

This year I am doing a Rhein and Mosel tour and only a week to go!