We've used Dollar multiple times over the last 20 years and have never had a problem with them. We also use Alamo & National...just depends on who has the best rate.
The thing to remember with Dollar, is that often, 2 (or so weeks out) you can get a great price without any codes.
I have a reservation right now for April 28 - May 2 for an intermediate car that started at $157.96 (total - all fees included), changed it to $126.52 a week ago, then today (on a whim because I usually don't check weekends) I was able to lower the total to $102.34 (all fees included)
What I don't like about Dollar is that you can't add an extra driver without paying for it. Other than that, we've had great deals renting from them.