Apple has started to send out sixth-generation iPod nano units to customers participating in the Replacement Program for the first-generation iPod nano. One iLounge editor yesterday received a silver sixth-generation unit as a replacement for a first-generation unit via the Replacement Program, a change from earlier replacement units, which appeared to be refurbished first-generation models. The shift to newer replacements will likely thrill many customers, but for collectors, it may be cause for hesitation, as it has yet to be seen whether Apple will once again start to send out first-generation replacements as they receive the faulty units. Apple launched the replacement program last month as a way to deal with potential safety risks caused by faulty batteries.