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There is debate on this topic, especially in game console repair. I think the conventional wisdom is that leaded solder is more pliable than lead free solder, therefore it is less likely to crack during repeated cycles of thermal expansion and contraction (or physical stress from dropping). The EU passed the RoHS (restriction of hazardous substances) directive a few years ago, so it is unlikely that new electronic devices will be constructed using leaded solder.
However, the EPA conducted a Life Cycle Assessment study to compare the environmental impact of different types of solder. In both paste and bar solders, leaded products had significantly greater environmental impact. Exposure to lead is no joke, so it might be something you want to consider. http://www.epa.gov/opptintr/dfe/pubs/solder/lca/index.htm
I wouldn’t worry too much about using lead free solder. Hundreds of millions of cell phones have been made for over a decade using it, and it hasn’t been a problem. In light of the amount of hardware that goes into landfills instead of being properly recycled, I'd say the move to lead free was the proper decision.