I've had these for a while now and feel like I can share my praises of them. First and foremost, I bought these last November for my future (soon hopefully, I just submitted payment) FM126 build. I did not expect them to come so quickly, nor to actually be riding them, but I've had them on my gravel bike for some winter miles on pavement. They feel insanely quick and insanely light, but again, I was riding a carbon gravel wheelset so that's kind of obvious.
I ordered the 50mm wavy, 25mm internal hooked width, with pillar spokes. I got a black friday discount, and asked for cheaper/slower shipping options (got laughed at for this, but you're welcome), and paid $531 with tax and shipping. Out of the box, the hubs were pretty quiet and didn't sound like the youtube video posted. I asked about this, got a quick reply that it was expected and the SR249 are quiet hubs, and was fine with that. After a few hundred miles, they are definitely quite a bit louder. I still don't care, but just something to note. I've been riding these in crusty conditions (New England USA winter), so I'm guessing there's probably a little gunk in the hubs. I had some issue with the tubeless setup but after dealing with slow leaks for a while, I just redid it, this time double taping the rim, and now I have no issue. I've noticed a lot of brands give the bare minimum amount of tape, so I was pretty thankful to Serenade for actually including enough to have some margin for error. Thank you for the support, Marya!
I have 32mm GP5000s on and the bike just rips. My gravel bike is a Specialized Diverge with a mechanical SRAM Apex 1x11, which IMO is an amazing bike, but is a bit boring in terms of stability and comfort. The wheels are giving me a surprising amount of zippy feeling.
I think the real test will be how they come together with the upcoming Mondince FM126 - I'll probably follow up here after that's all together.