When I looked up my GMail account this morn morning I saw that they activated the GMail phone feature for me and so far it is looking much better than Skype. These are the per minute call rates to a landline to Slovenia.
Skype (PAYG): 0.041 GBP/min
Google Voice: 0.026 GBP/min
Prices above include VAT and were taken from the Google and Skype websites on 27. August 2010.
Limitation with Google Voice at the moment is that they let you add funds to your account only by $10 ONLY exactly.