I think those that are unhappy tend to be very vocal. They feel, and rightly so, that after they paid for a new unit, it should be basically flawless.
That said when the complaints follow a particular brand very heavily, you have to ask if there is a reason. You likely have been lucky, but if you prefer to handle small stuff yourself rather than hassle with going back to the dealer you have made the majority of the issues moot.
Many folks may be willing to handle a few small things themselves, but when there are a couple of major items, the aggravation levels overflow, and then every minor thing becomes a major issue.
