I believe the turnpike is the only place where this has been implemented, and only in south Florida. I've never paid a toll in the Orlando area at which I didn't have the option of using cash or exact change. Be aware, however, that there are booths, especially at exit ramps, where your only option besides SunPass/EPass is exact change, so if you don't have quarters your stuck. And in that situation, you don't pay a hefty service fee - you get a traffic citation.
I read an article in the past few months saying that the fees rental car companies charge for the electronic toll systems can often be waived or reduced for the asking, and can also be disputed if not properly disclosed. (The implication was that they are frequently not properly disclosed). I have a philosophical opposition to paying for this, because the transponders are given away free by the expressway authority, and they don't charge any extra for using them. Indeed they give discounts to accounts that pass through more than 40 or 80 toll booths in a month - which, if it extends to rental car accounts (which I'm not sure it does), means that they pay less for the toll than they charge you - IE they make money if you use it.