Konrad Hofbauer wrote:
P.S. On Windows it is another story again (which I cannot tell).
At least with Uwe's installer (and I suspect this is also true for Joost's), it's a nonissue on Windows. By default, LyX will put the user directory for 1.5.x in <user>\Application Data\lyx15, and will put the user directory for 1.6.x in <user>\Application Data\lyx16.
/Paul
