First off, the size will mean this watch may not work for some people. Apple makes a small watch that wouldn't work for me, so this isn't just some issue that they created with the Ultra. The fact is they make watches for everyone, even if one of the particular watches in their lineup may not work for you.
This watch is definitely bigger. I personally see this as a benefit. Bigger screen equals a watch that is easier to see. This is especially helpful with watch faces that have numerous complications.
The one thing that most of the tech reviewers that handled the Ultra in Apple Park complained about was the extra layer of titanium to protect the larger crown. Some thought it was ugly, but Apple isn't the first to implement such a design. Panerai (and probably others) have had that as a feature for a long time. It is practical for a rugged watch, so it goes along with the rest of the design choices.
It isn't round
1. Siri - I know she has seen some bashing over the years, but the implementation is the watch makes it easy to do just about anything. Launching apps, setting reminders, sending texts, turning on and off Hue lights, etc..
2. Music control - iPhone, HomePod, Airplay 2 devices, etc.
3. Remote app for controlling the Apple TV
4. Activity rings and stand up reminder
5. Seeing weather
6. Reading email
7. Listening to podcasts on the AW speaker
8. Controlling the shutter on the iPhone camera
9. Reading headlines on apps like Flipboard
10. Using voice to record memos for Drafts
Even beyond that is getting notifications. I have security cameras and it will send me a snapshot when it sees motion. Getting messages from my credit card company which can give me instant feedback if my credit card is getting unauthorized use. It is no different from your phone in the fact that it makes it easier to just see when things happen. You can then decide wether it needs to be acted on immediately or not. Of course, I only allow certain apps to send me notifications, so I am mainly seeing the most important stuff on my wrist.
Safety and Cellular
The Ultra adds a new alarm/siren that can be heard from 600 feet away. There is also backtracking, waypoints, etc. so you don't get lost. The screen is bright enough to be used as a flashlight in a pinch.
Of course, having cellular is not only a safety feature, but means you can also get emergency calls if you are out on a run and something happens back at the house. I personally have not turned on that feature, though I have had it as an option on my Apple Watch 4 and now the Ultra. However, it is there if my lifestyle changes.
My own likes
I also like the Always on Display combined with this bigger, brighter watch face. I can run different clock faces depending on what I am doing. For example, I was at a Symphony over the weekend and chose night mode, which illuminated the red, low power face. When I have music playing, I keep it on a modular face that will show the song name. When I am at work, I use one of my many Clockology faces. I have been messing around with a few of them with orange and orange accents, but even with my orange watch band, other face colors still look fine with it. As far as the band, I like it, but I am looking to get a silver metal band for more dressy moments. It also works fine with my Apple Watch 4 bands. However, this isn't my first watch with an orange band, so I just like the look of it.
My own dislikes
To Wrap Up
All in all, for me, it has been one of the more exiting tech products I have used in a while, so I am going to keep it.
All of the Appley stuff
Bigger brighter screen
more rugged design
Price (though, I was expecting it to cost more)
should work without the need of an iPhone
too big for some
needs option to send "now playing" audio to watch speakers