I got a second Deck yesterday. Basically, Valve sent out new units for devs who previously got a pre-production Deck, since the latter won't be compatible with future system updates.
The new one is a 256 GB model, so I had a chance to check out the differences between the 512/256 GB model screens, and also the differences between the pre-production model and the retail model.
The most important part first: the B button seems much better on the new one, and never got stuck. As I wrote way back, that was (and is) a pretty significant problem on the dev unit. The sticks also feel a bit smoother. Also, the button labelling on what I still call start/select is different, but I already knew that. Finally, at least in terms of input, I feel like the haptic feedback (e.g. on clicks) on the touchpads is slightly weaker.
Outside of those input differences, the only significant difference is obviously the screen. It has a few advantages, but overall I prefer the anti-glare version. The tradeoffs are really the same as always with glare vs. matte screens.