I got the pre-emptive head gasket work done ($1100) as well (@107K). I have '98 Outback (both my dad's '97 Outback and my friend's '98 Outback had their head-gaskets go out at 98K) so their problems were a wake up call for me.
Hopefully, our Suby's will have no head-gasket issues to 150K and beyond....