My friends have been trying to convince me to get a Macbook for years. Nice way to start
It happens, particularly with products early in the cycle. The thing to remember is that all manufacturers ultimately use the same parts, and the same factories in China. Thus, Apple failure rates are about average. The totality of the OS X and Mac experience should be positive, however.
Hopefully all will be well with your replacement. For me, the value of OS X shows when it comes time to replace your Mac. Migration Assistant makes moving data and applications over to a new hard drive a breeze. No registry to deal with. No need to find old CDs or installation files. Just connect the two together (or connect them to the same network), and run Migration Assistant.