It is an axiom in industry that the first introduction of a product has more problems than subsequent editions; simply because in house testing cannot reveal all of the unaticipated problems that field use by hundreds of thousands of real customers will turn up. Since the design of the second edition of a product has the opportunity to benefit from all of the consumer complaints and service history of the first, the second and successive editions of a product typically get progressively more reliable, until a major change is made which returns the product to an untried first edition again.
This is well known with automobiles. It's not a given that the first generation will have problems, only that they will have more problems on average than subsequent generations.
For example, the Mac Mini seems to have been solid right out of the gate (with the exception of the mysterious "dim screen" effect on VGA screens.) However the iMac G5 suffered from many problems in the first release, somewere up to a reported 30% repair rate, mostly to do with overheating of components and defective capacitors. Second generation brought this down to around 10%. Presumably, the 3rd generation (the iSight model) will be more reliable yet, with a redesigned case and cooling system.