MSR rules the expedition stove world for good reason. Their XGK and WhisperLite models are far and away the most popular stoves on Denali for one simple reason: bombproof reliability. It doesn't hurt that they're intelligently designed all the way around. The XGK in particular is overkill though for anything short of expedition use, and for sheer convenience it's hard to beat canister designs.
The Reactor is one of their more recent designs, although it's still been around since about 2007 or so. It's a canister design, not the most appropriate for very high altitude and very low temps - i.e. Denali - but perfect for just about everything else; no schlepping liquid fuel and a funnel, just plug and play. It's also available in three pot sizes: 1, 1.7 and 2.5 liter.
One 8oz canister of isobutane will run for at least an hour, and you can get a lot of heated water and one-pot cooking done due to the quick boil time, on the order of 3-4 minutes starting with cold water thanks to dual action convective and radiant heating. Canisters and the burn unit stow inside the stove, which weighs just over 1lb 3oz naked. Smart design features include a transparent plexiglas lid with drain holes, flip-out handle that doubles as a lid-keeper, and even an included pack towel.
Two more advantages of canister stoves is that they are inherently windproof and you can hang them, for which MSR makes a great tiny, lightweight (1oz) hanging kit. Need a final reason? The Reactor is quiet, so if you're thinking you're going to romance your date over the afterburner sound of an XGK, think again and go with the Reactor. If you really want to cook food on your stove, you probably want the simmer control of the Dragonfly, but for the rest of us who boil water and pour it into things, the Reactor will do everything from date night to serious mountaineering and backcountry trips.