i am with powergen and have been for years.....they constantly work our bills out wrong, and despite me giving them readings they always give us an estimated bill.
i went on uswitch and it claims npower can save me nearly £200 a year (based on a years worth of usage, with accurate readings) but they only got two stars for service.
to be honest i don't see how they could be worse than powergen and if they really can save me that much money, i can live with a lower standard of customer service.
thought i'd get the opinion of mumsnetters on this one!