The paid version I have for a UK specific and the new iPad widget one is pretty much bang on, rain predictions etc. But then I use that info a lot for my activities and I like the rain radar option. There is a non paid version that lags by 15 mins, less features etc. I suppose it all depends on what weather services your country has.
I understand that the UK met office, BBC, Netweather etc. use different supercomputer models and use them to generate the forecast. I have found a discrepancy on the accuracy of the usual suspects in the UK but then it is a forecast, and one day one will be right, another the other model will be right.