I love my pellet grill. I do not have a Traeger but some general comments:
IMHO -
1. I look at mine as a wood fueled stove. Anything you can cook in a propane stove, you can cook in one of these, with the added bonus that you will get some added smoky flavor. It's temperature controllable from very low to pretty high and it stays at the temp you pick very nicely. As SuperDave said, pellet grills do not give the heavy smoke flavor many people like (as from a real wood smoker) but I think they are great for general use.
2. Get one with a digital controller. These allow you to control the temp much more exactly.
3. They seem to work best when you want to cook something slow - ribs, pork roast, tri-tips, etc. I cook ribs in mine for 6 hours and they turn out great.
4. I agree with those who say they don't give a great sear on steaks - although there are ways to get that accomplished. I do it the simple way and just carry a charcoal grill along with my pellet grill for steaks and burgers.
5. Costco was selling one of the Traeger grills a few years ago and still carries Traeger pellets seasonally I think, so I would look there for a good deal if still interested in a Traeger.
6. They are generally very heavy. My small one still weighs over 60 pounds, if I recall. For camping use get one of the small ones that are built for travel.
7. If you have a local BBQ store, they probably carry pellet grills and very often have food demos on a Sat or Sun afternoon. Maybe contact one and ask ?
You asked about cost -
On edit - My Green Mountain Grills Davy Crockett WiFi model is on sale now for $350 (per the GMG site). That is for sure the cheapest I have seen them - and less then I paid for mine. This is their smallest model - runs on 110v or 12v.