Ive had this grill for about 6 months. Cook on it all the time. Also have a Weber gas grill and a smoker. This grill is halfway inbetween the other two.
The pros: That said, as a result it is light and easy to move around with great wheels unlike some other grill behemoths that require a crane to move. I love the pellets which are cheap and easy to order online (dont order the traeger brand, it is like 20% the species advertised, and for the same price can get 100% from other sources, and package shows up right to your door). The $20 worth of pellets give about 20 hours grill time for about $1/hour. You can easily see how many pellets are left by lifting up hopper lid, way easier than with propane guesstimates. The best thing about the traeger grills is that they NEVER catch your food on fire. You can cook your roast overnight without checking it once. It will be fine. Think of it as a oven with smoke flavoring that wont stink the house.
The cons: It has a maximum temperature of maybe 375 if you never open it, and 325 if you check your food frequently. It just doesnt make enough heat and has thin exterior with no insulation, and not enough mass to maintain temp if you open the cover. Anything you cook will barely have any searing marks, kind of looks baked at low temperature. As a result I often brown the food on gas grill and then switch to the Traeger. It wont get hot enough to self clean. If you do salmon and dont change the aluminum foil and brush the grill (five minutes total) and then make beef jerky it will taste like salmon. (ask me how I know. the dog still loved it though). Some people have reported mechanical breakdowns. I havent had any, but do try to keep it covered (its still been rained on a few times, but mechanically and cosmetically still perfect).
What it does great: bacon (wow), ribs, breads, vegetables, jerkey, slow roasting meats already browned on gas grill without fear of catching fire
What it cant do: hamburgers, hot dogs, searing steaks (just cant get hot enough)
What it can do but I prefer to do on gas grill: chicken, fish
Update: Am cooking a whole salmon in a 40 mph snowstorm in 25 degrees here in chicago. My Weber Platinum LP grill blew out 4 times in 30 minutes. Switched to the Traeger. It hasn't blown out yet. Sweet! The salmons almost done. It is maintaining 350 (set to 375) but Ive only opened a couple times.
In short I think it makes a great second grill. Too many things it just cant do to be primary grill. I wind up using my weber gas grill 60% of the time. What it does do often just cant be done on a gas grill. Convenience vastly exceeds all other forms of woodburning stoves but some reports of mechanical breakdowns. You can make a complete meal on this grill, I do it all the time (set to 350, throw on some buttered asparagus, biscuits from those cardboard tubes, and meat of choice: BAM done with no dishes).