The nice bonus of these things, at least in Portland, is you're allowed to pay once and use the same sticker for multiple stops. If you have to stop 3 or 4 different places downtown it's convenient to only have to pay once for as long as you'll need to achieve all three tasks, and not need to dig up change for each stop or throw away unused time at each meter.
When they don't work, it's a pain, but the old style meters I had to deal with in San Diego didn't work frequently, and I had to get back in my car and move it to avoid a ticket. (Yes, I know they're not supposed to, but how am I supposed to prove the meter was broken?)
Living on Earth may be expensive, but it includes an annual free trip around the Sun.