I've played around with this in the Steam Beta, and so far, Valve has demonstrated the most stable and customizable use of Joy-Cons on PC. It is a mess right now, but I like what's presented so far. Also, current state of beta messed up all other controllers, as betas typically do.
Impressions
First off, depending on the number of Joy-Cons connected, Steam is abl eto either keep each other horizontally separated or combine the two into a pair.For now, two independent controllers cannot be set up, but there should be a "toggle" by next beta push to allow this.
The control stick forward axis (AKA which way is up) is automatically oriented properly for each left/right/both possible controller set up, which is neat. Most software programs on PC just assume they're always paired, or their native drivers assumed they were separate and not analog.
Configurator
The controller configurator in Steam for Joy-Cons is kinda weird; Steam may think you're customizing a Steam Controller, and I think this happens because, with the added gyroscopes and SL/SR buttons, the layout which the Joy-Cons must follow cannot be a simple Xbox because it would lose all the extra features.
| --- | Nintendo | Xbox |
|---|---|---|
| Gyro | Yes | No |
| SL/SR | Yes | No |
At the time, I guess Valve didn't have time to have a Joy-Con layout in the configurator, so they have the controller default to a Steam Controller layout, because this also has a gyroscope and additional programmable back buttons, unlike the Xbox.
Where is the X button?
| . | ^ | . |
|---|---|---|
| < | X | > |
| . | V | . |
When the configurator isn't breaking, it takes some patience to not only recognize what is meant by where buttons belong (especially when horizontal Joy-Con, it's very confusing), but also what is the intended button layout for the face buttons. X is X, but X is on top when in a pair and on the right when horizontal, or if focused on an Xbox legacy layout, it may be on the left. And last possibility, forcing a Playstation-like layout puts X on the bottom. That meme is in full force here.
| Pair | Sideways | Xbox | Playstation |
|---|---|---|---|
| ^ | > | < | V |
Some things are missing, too; when in a pair, SL/SR cannot be mapped, and the inverse is true for ZL/ZR/L/R when horizontal. Gyroscope fails to map as well, so I didn't bother testing the controllers with any FPS like Portal or BPM: Bullets Per Minute, hopefully that gets resolved. After all, if the Joy-Con pair is treated like a simple Xbox controller, nothing has changed with Steam's implementation because may other programs have already done this and players are simply happy about it.
When gyroscope finally works, it needs some tweaks too. Which camera axes will gyro movement follow, which controller in a pair will be used for gyro, or can both be used? Can gyro be used horizontally?
Joy-Cons as a Mini-Gamepad
A horizontal Joy-Con works pretty well for simple games like Spelunky and Necrodancer. Almost beat Olmec and Dead Ringer on first try. And I'd imagine the initial wonder of free-handing a pair of broken-off controllers like what everyone did with Breath of the Wild can happen dozens-fold with all the free-roaming exploration games on Steam.
Sticks
I did the stick calibration in the settings, and made sure the deadzones in each configuration were generous. "Stick drift" is about the same as on Switch console, even more manageable in Steam.
PS (post-script)
A toggle to switch Joy-Cons from pairs to separate has been added, Gyro has been added with calibration steps, and layout now mimics a Pro Controller, likely for stability. Still needs an independent layout for split Joy-Cons.