I have always used cash or bank account money to buy my bikes, occasionally use the credit card for parts, etc.
I do think it would be nice if there were more options for longer term/lower interest loans exclusively for bicycles. Then again, from a lender's perspective it's almost like a signature loan - bikes can be 'stolen' pretty easily and that would make it hard to repossess, so it goes back to the individual's credit to say if they are likely to repay the loan. It doesn't seem like there's much to be done about that, either - short of giving all bicycles a VIN and making them mandatory to register with the DMV, requiring insurance, etc... sounds like a pretty painful option to me.