The most N900 faults have been software issues, which (mostly all) can be solved with firmware updates. However, the first batch of the 3GS had a dump chipset position (in order to minimize the design as much as possible without skipping some necessary parts), which often caused overheating. It might be history by now, but how as a consumer are you supposed to know that, when Apple never even admitted the issue in the first place (now that it's fixed they could at least admit it, but no... we prefer silence).