Nobody knows anything about them, generally. I had a 2010 Supercharged and LOVED IT. I would have another in a heartbeat.
The L322 is a BMW design that was more or less built by Ford. Avoid the 2006 models, which is what Doug DeMuro had and mislead people on. The 06s are known for being pretty crap compared to 07-12.
2007-2009 are the most reliable option, they run the Jag 4.4L (if N/A) or Jag 4.2L (if Supercharged). The 2010-2012 have the Jag 5.0L in both N/A and SC form. It is NOT a Ford Coyote, but was developed using Ford money. It's direct injected, and can have timing chain guide issues. Long-specified oil change intervals lead to the plastic guides breaking down and then you're in for a big bill. The safest way to avoid that is to buy a 2012, as the 10s and early 11s were what was affected. My 2010 had 105k miles on original guides, though, and I was never too worried.
They all have Bosch electronics and a lot of FoMoCo stamped on parts. They are pre-wired for a 7-pin tow harness but you have to buy the stupid $100 part and install the connector. I towed my racecar with mine, and it was very happy to tow things on an open trailer. The chassis is too small once you move to even a small enclosed (mine is a 20' aluminum) - not enough wheelbase combined with soft suspension was not a fun time.
Speaking of suspension, the air ride is not super scary to deal with. Arnott and Suncore make aftermarket shocks/struts/whatever so you don't have to deal with OEM pricing if one fails. They do not seem to fail at the alarming rate of earlier LRs, and the best way to keep the airbags healthy is to cycle the ride height every so often. Mine worked flawlessly. You can trick it into giving you a few more inches of clearance off-road, too.
The 2010+ have a full digital gauge cluster, which is cool but kind of useless, as it just replicates round dials that you'd see anyway. The infotainment in all of them is pretty basic. Mine had the Logic7 sound system which kicked some serious ass.
2010-2012 S/C models have Brembo brakes with six-piston fronts. You cannot easily fit less than a 20" wheel to those models because of the caliper and rotor size.
These are heavy trucks. Mine weighed in at nearly 6,000 lbs. They will eat tires and brakes as a result. Typical to any BMW-based vehicle... front lower control arms are a wear item (bushings) so if you test drive one and hear it clunking around up front, that's what it likely is. The 5.0s can occasionally eat water pumps but they are not a strict 100k maintenance item like some BMWs can be.
I had all the records from mine, and it never needed much from what I could tell. I put 10k miles on mine in six months and it didn't go through anything weird in that time. Bought at 94k and sold at 105k, only because I needed a beefier truck to tow my new-to-me enclosed. I would have another in an instant. I towed the M3 with it, took it off-road a few times, and drove it daily to work and on road trips. It got E36 M3 MPG in the city (10 was common) but did okay on the highway (14 towing, 19ish unloaded).