the big question is WHY??? Unless there is some strong legal reason for you to switch, why bother? the net effect on the environment will be NOTHING! Lead free is harder to use, needs more heat and makes poorer connections. No gain for less performance.
Because its a potent cumulative poison and lead-free solders are perfectly easy to use - you set your iron for the correct temperature and _use enough flux_. Nearly all problems with soldering are solved by using a hot enough iron and enough flux. I've used both leaded solder (years ago) and tin/copper and tin/copper/silver solders more recently and there is no difference if you can solder properly and _use enough flux_.
As for the net effect on the environment go and take a look at the people in India / Asia / Africa recycling precious metals from circuit boards and the fumes they breathe every day(*). If you want to use lead, you are morally obliged to recycle it yourself I feel.
The only valid worry about lead-free solders is not the points you make, its the long-term reliability issue with tin-whisker formation.