I havent tried HP in my P1 as everything I read noted that it was a military design intended for a certain weight of 9mm ammunition (124 gr., I believe) and should be used this way. I didn't buy mine as a defensive weapon so much as I was interested in the design and its history, so am content to use ball ammunition. I would say that the trigger is not comparable to a modern firearm but is sufficient for me to hit falling plates without a problem at 25 yards. The P1 certainly is on the large side for being a carry piece, although there is no reason to not use it for this purpose with a suitable holster. I doubt you could find a really satisfactory IWB holster, although they may be out there. It would be fine in the same kind of flap military belt holster the P38 was carried in for many years in many countries.
I would not hesitate to use the P1 in as a defensive pistol, but there are so many other choices in modern firearms it wouldn't really make sense. All in all I am delighted with my P1 and often take it to the range, but I regard it in context and do not expect performance from it like from a P99, for example. The prices for this pistol are so reasonable these days I urge everybody to pick one up and am considering getting another at my local Gander Mountain just because I think it is such a great value.