Does anyone have any info on the katadyn?
Which Katadyn??
I have the mini and it's a good filter, it is not however a purifier (neither are the pocket or exped filters), so if you have not the time to boil, then chemical purification is going to be the way to go.
That I am aware of all of the Katadyn silver impregnated ceramic filters will filter down to 0.2 micron.
The mini Kat has a filter life of approximately 7,000 liters and the pocket filter an approximate life of 50,000 liters. flow rates are 0.5 litre and 1 litre a minute for the mini and the pocket filter respectively.
For both you can get replacement filters and both are field cleanable. Maintenance is a doddle.
If you are looking at just drinking on the move then a Katadyn bottle may be worth looking into, they make them in 2 sizes and although I have only ever used one once they have been highly recommended to me before now.
I would go into the benefits of the exped model, but I think it may be a bit overkill and I think the cost may seem prohibitive (especially if you have a £50 budget).