I guess we should aim for operation under:
1 all common Linux and nix's in general (which hopefully we have already as we don't do anything non-standard)
2 OS-X (i.e. BSD Unix with bells)
3 Windows (windows command prompt - eeek) - XP and onwards, not that the windows version should make much of a difference, hopefully...
4 and Cygwin on Windows (possibly if this works the direct windows support is less of a big deal)
1 * 2 are primary goals, hopefully with 1 and 2 we get 4 for free, then that leaves 3 as perhaps something to aim for over time
To be sure of 1 & 2 (&4) we need to do more testing. 3 definitely won't work without changes which might cause regressions on the other platforms if we're not careful