I did purchase a Ruger LCP to have while I am saving up the money for a Kahr PM9. I have grown quite fond of my LCP and have sent the slide and barrel off to Robar to have their NP3 finish applied. I think anytime you can upgrade to a 9mm over a .380 you would be wise to do so.
Having said that, my LCP will be my "always" gun, meaning there will be no excuses for me to be unarmed in the future. I can certainly understand $700.00 (Kahr PM9) versus $330.00 (Ruger LCP) in this economy nowadays, but other than that the Kahr still gives you a better option for self defense.
So I guess what I am saying is get the Kahr PM9 if you can afford it, if not, the Ruger LCP is still a great second choice.