I was just reading an article on Tin Whiskers developing with non-lead solders. The military evidently is concerned about the reliability of non-lead solders:
Lead-free solder: A train wreck in the making - Military & Aerospace Electronics
This was a Military & Aerospace Electronics article from 2005. Have they improved the lead free solders since then? That makes me feel a little concerned. I don't want any tin whiskers developing under a very high power environment.