Can't answer about the rails. I've handled a few of the plastic Kahrs and they just don't do anything for me. Tried to talk myself into a CW40 buy just couldn't do it.
As for the prices; This is an interesting time in the product release cycle. The First Edition guns have just about disappeared, and the first black ones are just trickling to market. Due to this the prices have gone up a bunch in the last month or so. Where I was seeing prices of $550 or so on GB, they're now much higher due to lack of supply. Dealers are raising prices on guns they don't even have in stock. This is a long way of saying, whoever was offering them for $500 even a few weeks ago probably cannot get them for that price today. No harm, no foul, things change.
If I'm wrong please let me know. I might consider a 9mm today instead of a .40S&W "sometime" later this year...
Lastly, in my gut I suspect the distribution channels will open up after the SHOT show, which starts this weekend (2/1). At least I hope that's what's holding things up. I really, really hope that Walther and S&W aren't having "turf wars", with S&W intentionally being slow to market so they can introduce their own "slim" pistol.
-- Sam