Lithium ion batteries are largely made in Chinese factories. I doubt very much that Pentax makes any batteries whatsoever. Instead, they contract with a battery manufacturer to supply them with batteries imprinted with the Pentax name and model number. Then, they mark up the price. By buying generic batteries, you bypass at least one level (and mark up) in the chain from the factory to you.
Our S4i camera is brand new as well -- we have had it for less than two weeks. Because the generic battery has a higher capacity (750mAh) than the original Pentax battery (710mAh), we have been using it as our primary battery. We have had no problems so far. Also, I have not seen any rash of horror stories about people who have used generic lithium ion batteries. Instead, people who have used them seem happy with them. Why do youfeel it is important to usea battery imprinted with the name of a major camera manufacturer?