I’ve used 819’s on Hope Pro2 hubs on my hardtails for the past 3 years. They aren’t particularly light but they’ve proved to be reasonably strong and reasonably reliable. I managed to pancake a rear rim in Spain a couple of years ago (I think a loose spoke contributed), and the replacement rim now has a slight egg shape to it after a particularly hard day out in the hills last year, but hasn’t got any worse thankfully.
I also ran Mavic 823’s on my full suss. Bombproof but quite heavy, which were replaced last year with Stans Flow / Pro2 combo. I’ve been extremely pleased with the Flows, they are lighter than the 823’s and 819’s, and the wider rim works better with the type of tyre I run. My biggest gripe with the 819 is it’s narrowness.