My Yoder YS640 has a date stamp of 2-6-13, so I'd say it qualifies as a "latest gen" unit. I have put it through the paces cooking at least 35 different items on it so far, and everything comes out fantastic. Temps swings aren't too bad, no it doesn't lock on one temp and not budge at all, no smoker does. It stays pretty true to your set temp give or take 10-15 degrees in my experience. And as far as hot spots, those are pretty much solved. It does run hotter on the right side of the cook chamber, but by about 20-30 degrees most of the time, so nothing you can't live with. In some cooks it's nice to have the hotter spot if you need it. And the heat deflector goes right up to the front and back of he unit, so you don't have this large gap where you food just gets blasted with heat. It is hotter there, but I'd say better than most pellet units.
For sure get the second rack, you will regret it if you don't. I have the cover and insulation jacket. The cover is top notch quality and so is the insulation jacket. It does cook a little differently with the jacket on, so I still need to learn that difference.
As far as pellets, I order LumberJack in bulk. They are a great quality pellet and a very reasonable price. I also like BBQr's Delight, but their shipping rates are higher for me and too cost prohibitive. Since the LumberJack's come from Great Lakes Renewable Energy in Wisconsin, the shipping should be very fair for you. Here is a link to their site if you want a quote.
As far as the bad reviews, not every cooker is for everyone, but I think it is pretty clear that almost all of Yoder's customers are very happy with their cooker. They did have some issues at first and admittedly some will try to scare you off depending on where you read, but I would purchase a YS640 again in a heartbeat, or a YS1320, I love that cooker. Everyone at Yoder and All Things Barbecue are great to work with and will help you decide which cooker and features are best for you. Give them a call and they won't steer you wrong. And if you do have any issues, their service after the sale is unmatched. They not only want to get your unit up and running, but they want to know what went wrong so they can correct it on future runs if needed.
And, it's made right in America's Heartland, not overseas. The welds on this unit are works of art. It shows the care and precision they put into the unit.
Here is a Wagyu brisket I cooked on mine:
And 30lbs of some irregular cut pork belly smoked at 160* using LumberJack MHC pellets after 5 hours in the smoke. The smell was insane.
Some ribs (first cook on it)
And I highly recommend adding at least one probe port for a maverick or other thermometer so you don't have to run it under the door and mess with the airflow of the cooker and pinch the probe wire. I opted for two just to be safe.
Here is my unit.
If you have any other questions, don't hesitate to ask.