I've had a P345PR (safety model) for a little over a year. I'm not sure how many rounds I've put through it, but it must be over 500. I'm a big fan of Ruger products, and the P345 is (for me) the most comfortable, and accurate .45 ACP I've had the pleasure to fire.  I usually shoot the cheap stuff (Wolf/WalMart Winchester white box) but, with two exceptions, I haven't had a single failure to feed, fire, and extract.  The two exceptions were caused by the safety lever being slightly pushed down (away from the full-up "fire" position).  The P345 saftey requires very little movement, compared to other Ruger P-Series pistols, to disable the action. In addition, the safety is held in the fire position by spring pressure only--no positive detent of any kind.  
If you are looking for a .45 ACP plinker or even something for informal competition, the P345 would be a excellent choice.  If the P345 is to serve a primary role as a defensive pistol I cannot recommend it.
Except for the design of the safety, I would give the P345 my unqualified endorsement.  Because of it, I'm selling my P345 and will use the proceeds to buy a KP90D.  I haven't seen any mention of this issue elsewhere, so it may only be an issue for me.