I work for a voice and data cabling company...

Don't fix whats not broken. Cables rarely go bad. The rare occurrences can be fixed, but you really don't need to replace cable until it fails. Usually new standards come out faster than the cable will fail. As has been said, gigabit /CAN/ be run on Cat5e. Stop worrying.

Because ID10T's can install it. Its cross platform and easy to use. We use it to talk to my Cousin in Thailand or Korea. My Aunt and Uncle have it in Oregon. It is also able to punch through firewalls and NAT problems extremely well BECAUSE THEY USE SUPERNODES to connect the call.

Also here is a good "Whitepaper" on the skype protocall
http://arxiv.org/ftp/cs/papers/0412/0412017.pdf