I have seen as many complaints and successes with various equipment, and the gambit of setups runs wide. Two of the things that seem to stand out are people's trials with time and temperature with any given setup, and 'gettin' enough smoke'. Many of MES complaints I have seen trend toward the older models, and I have read about others toying and tinkering with different gadgets and mods to help - mostly temperature probes and smoke production and delivery methods.
So far with an MES 40 bought Dec 2014, I just don't see what all the fuss is about when it comes to those things. As-is, it's much like anything else as far as 'getting used to' using it and it really doesn't require tweaking the setup with an array of other gadgets and contraptions to measure and/or maintain the exact temperature and produce the smoke. Just like a gas grill with burners, manual controls, analog guage and smoking with a tinfoil pouch, one just has to learn how a given apparatus behaves with given settings and conditions, and develop a feel for the timing as you go. For instance, I find that this MES tends to runs somewhat hotter than the temp set on its digital temp setting, maybe 10F on the low end and up to 25F on the high end, with a little swing back and forth. Just like anything else, its performance is of course affected by how long the door is kept open when tending. Using damp wood chips work just fine for smoke production in the cylindrical tray, just keeping them replenished as often as the smoke taste and penetration desired. Versus any other setup, it has so far proven to be more user friendly out of the box than anything else I have seen looking at the various rants, tweaks, and overall aspects of other equipment. Seems to me using the MES 40 is maybe more about just learning its behavior than sweating the variables and trying to adjust with a bunch of other gadgets and mods.