We purchased a Stoker half-way through this season and I absolutely love it! We use it to run all four of our WSMs at the same time, and it performs almost flawlessly for over 18 hours at a contest. I find that especially with the low and slow cooks (<50 degrees) it will keep temps within +/- 10 degrees for 95 percent of the cook.
It is also user-friendly. I pulled this thing straight out of the packaging at a contest in Waterloo, IA this summer. Within one hour I had it all set-up and it was cooking our overnight meats. We won RGC at that contest the next day, and won GC the day after that using it in LaPorte City.
I now have it set-up so I can control it from my iPhone and/or my laptop. The iPhone is great so that way when I wake up in the middle of the night worried about how my cookers are doing, all I have to do is grab my phone that is right next to me and I can monitor and control the temps from it.