I've rented in Bali and it isn't a problem if you've driven elsewhere in Asia (I have driven in 60+ countries so can compare). I think it is actually MUCH easier than India, Thailand, and a bunch of other places.

I strongly suggest using a driver in the dense tourist areas (as it will save a ton of time e.g. looking for parking) which is $10/day. Outside of these areas you might be better off without a driver if that is your style: more flexibility, privacy, lower cost, no need to worry about driver lodging/food. Get the IDL.