I've owned three sets of Joycons, four out of the six have drifted. I"ve replaced the sticks on two and sent one off for repair, all of them started drifting again later on. I've got a grey set that haven't started drifting yet, so I'm relying on those for the moment until I can be bothered replacing the sticks on the others again. They're absolutely a lot less reliable than any of the past controllers.

got 4 of em, no drifting

I've probably only used my joycons for about 10-12 hours total, since the Switch release, so i have no drifting. I pretty much only play my switch hooked up to my tv, with the pro controller, and i have no drifting with that.

Me and my two brothers all have a Switch, and all three of us had one joy-con drifting.

Brought mine back to the store when it happened. There, they told me that I'd get it back after 3 weeks if they could fix it themselves, or 6 weeks if they had to send it to Nintendo. I got it back after 6 weeks. They said it got repaired, but it was clearly just a new joy-con.

So how prevalent is this? RRoD level?

Switched the stick on my left joycon out last weekend. Cost me ~$7. It's an easy enough job, to be honest. While Nintendo should just make high quality controllers that don't break in a year, fixing them is relatively cheap and easy.

I have yet to personally experience this problem, thankfully.

6/6 drift for me. Some pull downwards, some pull left and right and some pull in 2 directions. It renders Mario Tennis Aces almost unplayable in multiplayer. Such a shame. My pink 1 was sent for repair and I still have an issue with it. Luckily I was given a years guarantee for the repair so I can still send it back. The issue was so bad for the green one that I actually snapped the stick off! Luckily I was able to pop it back in but had to get it in just the right position.

I haven't had the problem yet - though I did have to send the left joycon for repairs when the L button broke. I don't play exclusively docked, but the joycons only really get used in portable play.

the problem has probably been identified by this user https://imgur.com/gallery/58bBc43

as you can see the analogue sticks Nintendo used seem to be very susceptible to wear of the contact plates, which leads to the miss-input experienced as drift

that means all devices this type of stick is used in will sooner or later show the problem, depending on useage, but it also means it's quite easy to fix by installing new ones