I use an IQ110 with my Webers. I don't have any experience with other temp controllers (other than watching a friend of mine use the stoker at a comp), so I can't say anything about them. But here are my thoughts on the IQ110.
Pros: cheap, easy to use (once you learn how to use it), holds temps fairly well (within ten degrees either way) when it gets set
Cons: you need to become familiar with your particular controller
When I first got mine, I read the instructions and fired it up for a dry test run on my smoker. I had my Mavericks reading temps as well to see how accurate the IQ was. What I found was that the IQ110 is not calibrated particularly well. I followed all the instructions and had set the unit to 250 degrees. When the light indicated that the smoker was "at temp," I checked my Mavericks and found that the smoker was only at 215 degrees. The IQ110 temp probe and the Maverick temp probe were placed on the same grate about two inches apart. I waited about thirty minutes checking temps every five minutes or so, and the Maverick showed that the smoker's temp stayed around 215 to 220 degrees. I had to adjust the IQue to about 275 in order to reach the desired temp of 250 on the smoker's grate.
I checked my Mavericks for accuracy afterwards wondering if, perhaps, they were at fault, but they passed the boiling water test.
I then asked a couple friends of mine who bought their IQ110s a long time ago, and they both said that they had the same issues.
I guess the IQ110s are either using chips that are incorrectly calibrated or there are problems with the temperature probes. But for mine to exhibit such issues brand new out of the box (as well as confirmation by others) leads me to believe that the fault may lie with the controller unit rather than the probe itself.
Like I said, once I learned that I had to adjust the controller to reach my desired temp, it held it there fairly well. I've used it for a few cooks afterwards when I needed to do overnights or whatnot, and it does its job. Just be forewarned that you should test it and check the unit against other thermometers to be sure. Even with the new IQ120, I would still check it against other reliable thermometers like the Mavericks.