I'll put in another plug for Rec Tec. I've had mine since February. I have not had any temp swing issues with this grill at all. The set temp and actual temp on the grill always are within 5-10 degrees of my Maverick probes (one at grate level and one hanging about 6-8 inches above the grates in the middle of the grill. The maverick probe temps always show rock solid and do not swing more than a few degrees during a cook. I have had a few problems with keeping low temps this summer. When it is 90 degrees or more during the day and in the sun, I have had to crack my lid open just a hair to keep temps down in the 200 range. Without cracking the lid, I had a hard time keeping temps below 240. I could change my auger speed settings and slow it down in order to get the lower temps, but then I will just need to adjust them again when the weather cools a bit. . . . . . not a big deal.
I won a Traeger Texas Elite in a raffle shortly after I bought my Rec Tec and gave it to my mom. She loves it and cooks on it all the time, but the temp swings I see on it are ridiculous. It can fluctuate as much as 50-75 degrees in a 10 minute time span.