I've been using it for about a month.
I like the fact that it automatically turns off my wifi when I leave the signal area and turns it on when I return. I have Tasker and it had a similar feature, but wasn't as reliable.
JD will also turn off your radios when you put your phone to sleep and then turn it on a predetermined intervals to check for info. It doesn't always reliably turn it back on and connect though, so I have it set to keep wifi on at known wifi locations when asleep.
I think it saves me power. When asleep and not using wifi my phone uses 1-2% per hour.
I'd be interested to see if anyone else has other apps that work as well.