I have a P4 and like it. The pliers aren't up to big jobs, but they are OK as tongs and for things like cutting and bending safety pins. I was surprised at how useful the small philips screwdriver is. It often fits where one from the bigger tools won't.

I also have several in the Juice range, and currently every-day carry a Juice Cs4. To some extent bigger is better, but I suspect the cases where the P4 is inadequate but a Juice sufficient are rare. Generally if the P4 can't manage, you need something a lot bigger rather than just a little bit bigger. Eg for opening packages, in my experience there's not much difference between the blade on the P4 and the blade on the Juice. For a real cutting job I use one of my Ritters.