In reply to Roberttaylor:
I've been on a few Greenland expeditions where the fuel used was A1 Jet (a kerosene based aircraft fuel). Various team members had a variety of stoves between them including a WhisperLite and a DragonFly but the first never functioned properly and the second had problems. The only stove that was completely reliable burning this sort of fuel in sub-zero conditions was the XGK. The WhisperLite is cheaper but doesn't really work well on paraffin in my experience and the DragonFly simmers better than the XGK but seems more temperamental when conditions and fuels get tricky.
The new XGK EX had to be produced apparently as the older model could not fit inside a GI's helmet which gives you some idea of how many of these MSR probably sell and the sort of conditions they are designed to be used in.
Two of the great advantages of MSR stoves are the shaker jet system, which means most blockages can be cleared without turning the stove off, and the cut cable that lives inside the fuel tube and works a bit like a pull-through in a rifle, which means (if you pull it out and clean it regularly) you shouldn't get any blockages of carbonised gunk in the pre-heating tube. Having said that, I'd still take spare jets and prickers, along with o-rings on any trip. Maintaining the thing in the field is simple though it's best to go through it all in advance so that you are totally familiar with it.
Mine is an older model which has given years of good service. Having tried various other stoves, I wouldn't take anything else other than an XGK on an expedition.