Well it took me a day to lift the machine out of the metal crate, assemble, check all bolts for tightness and lube all zerk fittings. Called Betstco for missing engine manual and grease cup for one wheel. Second day filled with 5/30 Syn oil, gas and did test run to set height, Found that with my Walnut orchard the lowest setting would work oK. Deck is tilted slightly forward. Third day mowed 5 -6 acres on one tank of gas in about 4-5 hours.
My wheels are mounted to the rear to he;p with tree clearance. Makes it more difficult to crank down the wheels. I think the extra grease that I pumped in there helped.
With my A-frame hoist I lifted the mower vertical to inspect for freedom of movement and wear or damage. All was good. I had picked up a few rocks that sounded like damage, but did not find any.. The sound was very loud when the hit.
I am very satisfied with the quality of the mow and the operation of the AT145 59".
Bill in Upper Lake CA

I have 59 inch version.
Reason being, I have 1/4th of my 6 acre as wetland, so no regular mowers really do much there, outside of getting stuck in mud. I chose to go for a tow behind then, as my SxS does not care about wetland, goes anywhere.
So, first thing first. I had it shipped. Shipping was very fast. Very. But be prepared for surprise. It's in metal crate. To get it out, you either have to hoist it up out of crate, or, cut the crate. Took me several broken hacksaw blades and several new Sawzall ones. Do NOT cut on welds, kills your blade. Cut crate on tow bar attachment side! Makes it easy to pull mower off wood pallet.
I then installed wheels right on pallet and pulled it off it. You may need to hook it up to a truck or something.
Now, engine. Manual is pretty useless. Oil is 5W30 and it takes whatever it takes by dipstick, with mower engine vertical. Get narrow funnel, filler hole is very small.
Engine started from second crank. Looks like it's regular carburated engine - choke, OPEN FUEL SUPPLY, pull cord, when it starts, open choke and add RPMs with silver lever. One thing that scares me about that engine, when adding RPMs, at some point it shakes badly, but then it all works fine.
I don't have battery installed yet, no comment on that.
Does not appear to be fuel thirsty, I just ran it for about 2 hrs on single tank - did fine. There is no fuel gauge, so how much you have left is your guess. Carry gas canister with you.
Mower is VERY heavy. But I like it, I like heavy for such equipment. Has 3 belts, that's good.
Now, mowing, as that's why we bought it.
Mows very well. I really like how it drops clippings down, instead of tossing them to the side.
I finally put it to real use today, caught not raining day. So it goes through tall grass, like it's not even there. I pulled it over puddles and mud, no problem. Cut is rather smooth and it does not miss much. I have 60inch ZTR and mow quality is better on flail.
It is hard to maneuver around trees and tight spots/corners. I have to do 3 point turn in several places of my property. It does OK. Hence, for my application, I end with some uncut areas in tight places, I'll either use trimmer or my riding mower to finish them. No big deal. But for large open spaces, that thing rules.
I'll eventually take Y blades off and sharpen them, they came pretty dull.
I left some very puddled/muddy areas untouched for now but, with my ZTR, it takes me 4.5 hr to mow my property. I did 80% of it today with flail in about 1hr 40 min. I am still learning how to route my runs, as I have trees, 2 creeks, hills, so it will take some time to figure most efficient route, without 3 point turns. I'd say, it should take me 2 hrs to do all mowing plus 40 min to finish tight areas. Should go faster once wetland dries out more.
2 biggest gripes I have for it is lack of fuel gauge, unless I missed it and ability to turn it off remotely.