Someone sent me a DM asking my thoughts regarding the monitor, and I figured that others may find them useful, so I'm repeating them here.
I have a Mac Mini M2 Pro and a MBA M1. However, I've never tried connecting the Air to the Dell -- it's been connected to the Mini 24/7.
I leave my Mini on all the time, as it's a Time Machine server for my Air and for my wife's MBP. I do let the display go to sleep though.
I connect the Mini via USB-C. I installed the Dell app, but nothing else (i.e., not BetterDisplay, etc.), although I don't really use the app for anything. I use the "5K color temperature" profile, which looks best to my eyes -- slightly warm. (The app was nice to cycle through the various preset color profiles without having to use the controls on the monitor, but once I found the profile I liked, I haven't used it.)
Have had no problems with the display itself. I run it at the recommendation HiDPI resolution ("looks like" 3072x1728). The display is always "found" when rebooting, and waking from display sleep is nearly instantaneous (my old Dell 5K monitor would take 10+ seconds sometimes, and sometimes the picture was messed up and I had to reboot the monitor). There's never been any issue in this respect, and that has been a godsend to me.
By comparison, I had issues with the Dell 5K, which connected via 2 DisplayPort cables. With my old Intel Mac I had to disconnect one of them when rebooting, and then connect the second cable back once I reached the login screen.
I am running Sonoma 14.2.1. My understanding is that Sonoma 14.3 enables HDR with the Dell over USB-C (whereas 14.2.1 and earlier only permit it over HDMI, which I haven't tried). HDR is not something I'd enable anyway, as I don't use the Mac for media consumption.
The display is anti-glare/matte, but it's a light touch and doesn't affect text quality -- it's not like the anti-glare/matte screens of yore that are awful. All things being equal, I would have preferred a glossy screen -- you do lose a wee bit of "pop" to the colors with the matte screen -- but it's not a super minor issue, and not worth spending more the 2x to get to the Apple Pro XDR Display. (The Dell 5K had a "light glossy" screen that I prefer, FWIW.)
The speakers are serviceable. They are nothing to write home about, but serve their purpose, and I'm glad that they're there. This was a dealbreaker for me with the Apple Pro XDR Display -- I didn't want to clutter my desktop with speakers, but still needed sound.
Someone else mentioned that sometimes the sound "takes a while to get going" for lack of a better phrase. I've noticed this, too. If no sound has been output for a while (say a couple of minutes), the next time sound is output, the first half second of sound may isn't audible. In effect, what this means is that sometimes the mail app "whoosh" sound may not be heard, or the paste sound in finder may not be heard. It's not all the time, and I can't discern a pattern as to why it happens sometimes but not others. And it's sufficiently intermittent. A minor annoyance to be aware of (though I don't know if everyone experiences it), but not a dealbreaker by any means.
The USB ports work. I connect my magic keyboard to the drop-down, front-facing USB-A port, and when needed charge my Logi mouse with the drop-down, front-facing USB-C port. I use one of the back USB ports (can't remember which) to connect my Logi webcam. I do not use any of the other ports (e.g., network port).
The webcam, to me, is awful. Full stop. Comparing it to my external Logi webcam, I don't like the brightness -- seems too washed out -- and sometimes the webcam would switch from HD to SD in Zoom and Teams, necessitating hard power-cycling the monitor to get it back. To be fair, I only played with this for maybe a couple of hours, but at the end of the day decided, I like my Logi webcam, so I decided to just use that.
I would love it if the webcam were detachable (or, better yet, if Dell offered a version of the display without a webcam). The aesthetics look silly to me having two webcams on the top of the monitor. But such is life.
I can control speaker volume through the Mac (including with the sound keys on the magic keyboard), which is a boon to me. I cannot control brightness with the keyboard keys, though (but can through the Dell app). That's not a big deal because I don't adjust brightness.
Overall, I'm very pleased with the monitor. It has great build quality. I don't have any issues with the display; the sound issue noted above is a very minor irritant; and the aesthetic of having a webcam that I don't use doesn't grate on me.
If the Apple Pro XDR Display had speakers, I probably would still spring for it, even though it's >2X cost once you add the stand. That said, the Dell gives you the same quality of panel to my eyes (but for its being matte and not glossy), with a price that is <50% of the cost.
The TL;DR is -- I would buy the Dell again in a heartbeat.
