> Sure, I don't think it unreasonable to require RHEL 6 rather than 5 now. Agreed. It seems like most setups get upgraded within 6 months or a year of the next release. So phasing out along that sort of time frame makes sense.
> >> I think the main immediate effect would be to update to boost 1.40, and >> gcc 4.4 > > Are you suggesting that users have to have the latest release of OS X on Mac? Right now things will build all the way back to 10.4 - although I'm not suggesting we need to support that forever - but I think it unreasonable to expect everyone to use Mountain Lion, for example. Snow Leopard is still at gcc 4.2, and a lot of people (even in the Sali lab) still use that. Just to add an *, it is a heavily modified gcc 4.2, I think (Mountain Lion's gcc is also 4.2).
I'm not saying we drop old versions immediately (nor that we go and break backwards compatibility out of spite :-).