I use GoogleTalk for one on one conversations, and I love it. Clean interface, good reliability, some great text features too.
Skype on the other hand has a interface straight from the book of 'horrible **** that got past the beta team', dodgy voice quality, and a generally annoying chat window. Most of it is just personal taste, but GTalk is just so much cleaner.
I'd go for a regular line if you need it for business, or at least make sure you're a paying customer so you can sue them. Watch out for the eBay sales calls, too. I reckon you read The Register? If not, look at their site and check the latest eBay/Skype stories.