My general rule for dependencies goes for the lowest version that will work. I start off with version '0', and then change that if I need something specific.

I try very hard to avoid using new features of modules just because I can. A lot of the people I work with can't simply install ne modules like I can. For that reason, I don't simply list the latest and greatest version on CPAN.

It usually takes someone telling me that my module doesn't work with some version until I change the pre-requisites. The tough part is that the modules usually break with later versions, not earlier ones.