Last night was not a good time to find out (though I guess I knew really) that an Endura Pakajak is not waterproof. At best, it is showerproof - any more than a light shower, and you are completely soaked. As in you might as well be wearing a jacket made from kitchen roll.
I had only got round the corner from Grosvenor Place to Buckingham Palace and the arms were completely soaked through and stuck to me. I was wet right through to the skin, including my padded bra top (ladies here will attest that isn't very comfy).
At least it was on the way home so it didn't matter so much.
I have one or two jackets and a trenchcoat that I know are completely waterproof - my trusty Altura Kinetic, and a Lands End ladies trenchcoat. But it is too warm to be wearing any jacket at the moment really.