I played Uncharted 4 and Ratchet and Clank, both games are sharper and the image is cleaner. But the biggest winner till now is HDR for me. The bigger wins for PS4 pro will come with newer games which can utilise it better than games that are backwards patched. I expect great things from Horizon Zero Dawn on PS4 pro, also Tomb Raider seems to utilise the pro pretty well.

I just played Titanfall 2, and holy Schnikes, does it look good. It's probably to be expected, considering the game was running at 900p before (and now supersamples from something higher than 1080p) but it looks absolutely gorgeous. It, Ratchet and Tomb Raider are the most impressive games so far. 

I notice the improvements to DriveClub too when switching back and forth. Image is a bit more stable and also the dashboard seems a little sharper, it's easier to read the speedometer from the same distance. It could be many things. Not the HDMI port yet there is much more going on before the image reaches the headset. The 60 to 120fps conversion likely benefits from the improved GPU, as well as the scaling engine that transforms the rendered image to the warped image that gets send to the headset. Headtracking might also be slightly snappier making the image more stable. With even faster load times, it's already a noticeable improvement without a pro patch.

I played Tumble again last night on the pro, also no patch yet. However the tracking seemed less temperamental than before. No issues of unwanted image shifts or jittery move controller, as long as I didn't move it out of view or in front of the headset. (Playing on the couch, make sure your drink is not on the arm rest! I tried to place a virtual block in my drink :/)

HDR is more work than a simple resolution patch. Increasing render buffers to 10 bit and balancing the output to a higher contrast takes more time. Hopefully devs see enough benefit in it to give it proper support. Unfortunately it doesn't show in screenshots and proper HDR tv adoption is even lower than 4K tvs. A friend of mine bought an OLED 4K tv last year, doesn't support HDR from the pro :( The tv promoted deep color as HDR at the time, not the real thing. Deep color is just 10/12 bit color, HDR is an extra layer on top of that to boost contrast range.

Hopefully next year HDR matures to a stable format and devs will have had some time to experiment, and perhaps the sdk will have been updated to make adding HDR output easier. I also wonder if Trackmania Turbo is going to be the only native 120fps game on psvr, or if devs will optimize for that option more often. Or at least put out some 90fps games.

Has anyone actually got HDR to work from a base PS4? I'm guessing you still need to hook it up to a 4K HDR telly (since no 1080p tv supports it), yet afaik 4K tvs only accept HDR signals over 2160p which the ps4 can't output? How is this supposed to work?

Based on what I heard from some playstation channels, the games that do support the pro only offer a boost in resolution and some of them do it at the expense of performance.

Yeah, I was playing Uncharted, Ratchet, TLOU,  and Infamous in HDR on the OG PS4 for about a week before I got my Pro. The games look amazing even on the OG unit thanks to HDR. The only issue is image softness, and shimmering due to the lower res. I actually am much more happy with Uncharted in HDR on the OG PS4, than Tomb Raider in 4K on the Pro. 

Like you said, it takes a bit more to implement HDR, but hopefully devs get on board next year. I absolutly miss it, escpecially in Tomb Raider and Titanfall 2. Both of those games have moments that would be brilliant in HDR, and its like, Wow, what could have been.

I played First Light with HDR on original Ps4 connected to HDR/Uhd tv. The colors are amazing. The settings on my TV automatically changed to HDR settings once i started the game.

When it comes to hdmi 2.0a, the cables and requirements I am still confused but it works with my older cables so I am not complaining.

Pretty much, some things deff look better, old games just play well just as you are used to, some games, like fifa 17 just run perfect on 4k, others, like skyrim and the last of us deliver the 4k experience but take a big hit in performance, the last of us used to be 60fps/1080p and on 4k with 30fps you do really get a worse gameplay experience for a better graphical experience, on skyrim, well, the game goes from a solid 30fps from the base ps4 to a 4k experience with more framedrops.

Other games, however, like Battleifled 1 and Titanfall don't go full native 4k, but use a dynamic resolution of around 1440P (the sweet spot for ps4pro it seems) and manage to improve the performance over the base model because the resolution might drop, but the frames won't as much as on the base PS4.

overall you can really see native 4k won't be used much but the bump in resolution is nice, for people that own a 4k television.

Personally I only played on the pro for 4-5 hours since I don't own one myself, but the two games that really did a good job where Infamous and Tomb Raider, they let you choose either a bump in resolution or a higher frames per second, and the higher FPS was really what I would want, the games got more responsive, played better and it felt like the experience I would want to play over the original.

But I am sad to see resolution (graphics) is prefered over gameplay (fps) by most developers and sony

Pro first and then VR. Pro handles games better, I hear.

You do however have the option for 1800p 60fps I believe, which is still a huge boost in resolution.