Just to chime in after my initial play session today: My gray left joy-con is definitely giving me problems after downloading the patch.
I've been using the grip while the system is 3 metres or so away and sitting docked behind the TV (which can't be avoided at my parent's place unfortunately), which I feel should be an acceptable distance and set-up.
Zelda became literally unplayable after the first 20 minutes or so when the left joy-con started to desync and then to refuse to resync or stay synced after I managed to sync it again by standing closer and/or removing the joy-con from the grip. Quite often Link would simply keep running in a random direction as if the analogue stick got wrongly calibrated all of a sudden, or all the buttons would suddenly stop responding alltogether while these syncing problems were happening.
Luckily I managed to snag a pro controller as well otherwise I would be quite pissed about this. Now, I'm mostly worried a left joy-con recall might be needed to fix the issue.