Go ahead and use your player. Mine has played everything great over the past 4 weeks that I've owned it -- mostly rental discs (thank you, Netflix!). I've also played some burned DVD-R home movies and burned audio CDs that my old regular DVD player couldn't handle. For standard DVDs, I'm really impressed with how well it upconverts to a near-HD experience.
Mine came out of the box with something like the 1.2 firmware and I updated it up to 1.5 about 2 weeks ago, and then today to 1.6. For some reason, I had to stair-step up one firmware version at a time, which takes over 30 minutes using the internet. Still, I've had no problems at any time playing anything.
The only thing to be aware of is that it turns on slow -- as if it's a computer booting up, taking maybe 20 long seconds before you can put a disc in.