No first hand experience, but I'd say it depends.
Will it get considerably better mileage or make large amounts of power over a well tuned carb, no. It is better, yes, but not by leaps and bounds. If you get an extra 2-3 mpg and another 10 hp out of it, how long will it take to recoup the $1000+ in gas savings, longer than you'll own the car. However, because of its fine tuning, feedback loop method, it can make more radical set ups easier to live with, as it will for any combination, and once you get past the set up and mapping, makes for easy living on more docile set ups.