I have a Steam Deck and I love it. I got the 256gb LCD version back in August 2022. The killer feature for me is portability. I find myself playing more games because I can lay on the couch or take it with me on trips. No longer stuck in front of the computer. The other awesome thing is the sleep functionality. You can hit the power button at any time and the deck will pause your game and go to sleep. Great for getting a few minutes in while waiting on the bus or while the kids are distracted etc.
The KDE desktop mode is fine. I don't really see people using it as a replacement for a typical PC/Laptop but the option is there. I use the desktop mode to install additional software and that's about it although I do nerd stunts occasionally like using the steam deck to control other equipment. It's useable with the touchpads but I use a bluetooth keyboard and trackpad when I do it.