I've had the PS4 Pro for the past 6 months and it's been nothing but a pleasure to use. Traditionally i've only ever used an Xbox for my console gaming but with the new updated hardware the improvement in graphics fidelity shows on the PS4 Pro.
Coming from the Xbox, the main thing I noticed is how fluid and responsive the OS is compared to the Xbox and how quickly you can switch from game->menu->game. For example, I could quickly and easily change my playlist on spotify and adjust the volume level of the music and be back into the game again without any lag. A downside is that the layout of the PS4 menus are slightly confusing and takes a while to get used to. Installing games is probably the fastest out of all of the consoles and games load fairly quick.
Gaming wise, a lot of games have or are being updated to work better with the Pro and the difference is night and day. This doesn't apply to all games but one of my favourite features is being able to switch between High quality gaming mode or High Frame rate mode. Some games just play better with high frame rate but for those games with a lot of detail it's worth switching to High quality mode to get the benefit of 4K resolution.
Overall I'm glad I bought the Pro because i've been introduced to an immense library of games and an improved experience.