I've cooked on a Slow-n-Sear exactly twice and if still had my Weber Kettle, this is the single piece BBQ I'd order without hesitation. In fact, a friend who I was trying to kamado cooking bought one and hasn't even considered a kamado since. To my mind, the Slow-n-Sear is a game changer for kettles on the order of magnitude of the Chimney or the rotisserie.
In both my cooks, we used a full chimney as the initial charge. For the butt cook, we got a little over 8 hours and needed to recharge with another half chimney. That was a nonevent as all we did was lift up the gate, pour in the KBN, recharge the water reservoir, put the lid back on and then went back to baseball and beer. It was great pulled pork and my buddy was hooked.
The other time was grilling steaks. In that application, the S-n-S did a bang up job. We reverse seared some 2" thick NY Strips that turned out perfectly.
When I get another Weber Kettle the very first thing I'm having delivered is a Slow-n-Sear. My experiences with my buddy's kettle has convinced me. I wouldn't be the least bit surprised to see Weber acquire S-n-S down the road.