I've tested Skype and have it on my system, but I use proper VoIP providers for my main use.
Skype is a pain in that you need a PC on to make and receive calls, really just a kids toy version of the real thing.
Use a proper SIP VoIP provider like
www.sipgate.co.uk and you can make and receive calls over your broadband connection without the need of the PC being switched on.
With Sipgate and other proper services, you can if you wish use software and your PC to make and receive calls, you can also use the glorified soundcards (USB phones - AKA USB toys), you can use a proper VoIP phone that connects to your broadband router, or like myself a ATA (Analogue Telephone Adaptor) that connects to your broadband router and you connect a standard corded and/or cordless phone to it, these latter 2 solutions require no PC to be switched on.
Skype charge you for an incoming number, Sipgate give you the number for free, you can choose any areacode, not just your local one, and you can call other Sipgate users for free and those of several other VoIP providers for free.