I've just purchased a Taurus PT145. I haven't had the chance to fire it yet and I'm getting anxious. I looking at this weekend. The one problem I can see right now is that the slide release is extremely stiff. I mean 2 thumbs stiff. Any ideas on making it a one thumb operation? Or should I just use it a while and let it loosen naturally?

It's likely the result of too strong a recoil spring. You can remove the top end, insert the slide stop in the frame and get a feel for how the detent pin is riding against the face of the stop without the added weight of the slide and recoil spring bearing down on it.

You can slip the bare slide on the frame and check the engagement of the slide stop in it's notch to see if either the notch or the slide stop needs a little stoning.

Or, just put some rounds through the gun and see what happens.