Thanks for some great suggestions! I'll definitely look at using Sort::Key::IPv4 in my own scripts.
The main reason I felt the need to post this was because I found the naive sort being used in a CPAN module, Nmap::Parser. I guess I expected a little better from something that gets pretty wide use. I figured it would be worthwile posting some good pure-Perl sorts, since module maintainers wouldn't have to add additional dependencies if they didn't want to. Really, why not use a drop-in replacement with almost 100% speedup?