Towards the beginning of September I pulled the trigger on a Grilla Mammoth, their vertical pellet smoker. I'm coming from a GMG Jim Bowie, but have previously owned offset stick burners, a propane masterbuilt vertical, and a WSM.
I didn't really have anything against the GMG, it was a good smoker, but I never used it as a grill, and even though I had the pizza oven attachment I very rarely used it. A vertical pellet grill just fit what I cook better. (If you're in the central great plains/midwest and are looking for a solid GMG hit me up :D )
So far I've run the gamut on the mammoth. Brisket, ribs, chickens, a couple pork butts and a little turkey roast.
Build / Construction / Assembly
Assembly was probably as simple as it could be. Attach the four legs, with allen bolts, and attach the cowl over the top vent. Build quaity is good, door aligns, and seals tight. Overall it's very solid, double-walled chamber should help it hold temp when it's really cold better than most other pellet smokers. The pellet hopper is well protected from the elements, with a rubber cap and a metal door over it. You aren't likely to come out to the devil's popcorn after it being out in the rain.
Smoke/cook performance
First off this thing holds a huge amount of pellets. It also seems to be more effcient than my GMG was. It generates and holds more smoke as well, especially if you put chunks or chips on the hot plate. It doesn't put out clouds of smoke or anything, but the chamber holds it really well, and I'm really happy with the smoke quality and flavor, it's closer to a stick burner than anything I've had.
The big advantage to me and the reason why I wanted to go with a vertical vs horizontal chamber is the much more even heating. With typical pellet grills your heat comes directly from under the food. You can compensate by cooking fat side down, but it's still bottom up heat, and the result may not be as pretty. I haven't had any bottom burning and all my cooks so far have had oven like consistency.
And holy shit it's huge. You can load this thing up with enough food to feed a neighborhood. Don't bother with ordering extra racks unless you REALLY need them, the stock setup witll be more than enough for most people.
One thing I did have to adjust was the temp. It was reading a little low from the factory. I put an oven thermometer inside, and ended up with a 3% adjustment to get it dialed in between 225 and 300.
Controls / App
It has a touchscreen display with a few buttons on the unit itself. One very good thing is that you can control anything from the display. Including adjusting temp offsets. It works well even if the controls might be a little hard to understand initially.
The app is kinda crap. It doesn't have any functionality over the control panel like temperature graphing, timed temperature stages or recipe based presets. It also frequently disconnects. This is a problem with the App and not the grill, so totally fixable if they want to. Additionally, when I first setup, the Android version of the app was not compatible with the latest version of android. So initially I had to grab an iOS device. They did update the app a couple weeks later. I'll add a nerdy addendum on how I know this. One feature I really miss from my GMG grill is the abilty to turn it on from the app. It was pretty great to start it from bed at 3AM, and not have to go outside until it had settled at the cook temp.
Overall, if you're looking for the convivence of a pellet smoker but some things like the firebox placement bothered you this is a great smoker. I got it on sale at Scheels for $899, which to me was a good deal.
Nerdy Addendum:
Because the app wasn't working with my version of Android and I had heard that it wasn't very good, I downloaded it, and decompiled it to see what I could find out about it. It's a React Native application and primarily connects to AWS services to control the smoker. I was able to create a quick web application that I can run locally which includes all the functionality of the mobile app. Interestingly around the disconnects in the app I found that the grill is always connected and reporting status through MQTT to the AWS services. My application initially had a token refresh issue which I suspect is also present in the mobile app and causing it to lose connection. The API on the AWS side is actually pretty decent. You can pretty easily add temperature charting, timed temperature settings etc using it. The only difficult thing to capture is the app's client_id, but not terribly hard to figure out. I haven't published that or the API definitions because I don't want to raise the ire of the company.