My wife and I are just back from a short trip. We haven't been tested yet, but we've been extremely careful at home and tried to do so in during the trip as well.
The good news is that everywhere we went, guest compliance was excellent (>95%). Even walking in from the parking lot to the parks, people were wearing masks. Another positive was that many things Disney is doing seemed very safe. For instance, ride queues were well spaced and outdoors to the extent possible. Also, the resorts we were in (CCV and BWV) were very quiet with few people and plenty of space. I never felt at risk at all in the resorts. We ate all of our meals outdoors and didn't really feel at risk at any of those locations either (Homecoming, Geyser Pointe, etc.).
The downsides were that distancing broke down quickly in the areas crowds were high and there was no structure imposed with floor markings. For instance, in the Emporium people were not very mindful of personal space, were free to move in any direction, and several people were within easy touching distance. Essentially it's a free for all in shops (except for check-out) and you cannot count on others to be aware of distancing. We experienced that at both World of Disney and the Emporium in particular but also in some of the other shops in the parks (resort shops were much less crowded).
The parks are at 35% capacity which doesn't sound like a lot of people. However, keep in mind that a lot of people-eating attractions and dining are closed (or low capacity) so 35% feels more like 45-50% in terms of the number of people just walking around. 50% capacity is essentially a pre-covid day in some of the parks (according to Len Testa and touringplans). Also, while overall capacity isn't terribly high, people do not spread out evenly across the parks and tend to congregate in the usual particular areas. New Fantasy Land on mid-afternoon Monday was essentially as crowded as it was pre-Covid, maybe more so with the queues taking up some of the outdoor real estate. Adventureland had dozens of people eating Dole Whip (maskless) right by large crowds of people just trying to get to where they were going. Galaxy's Edge and Toy Story land were also quite crowded. I wore an KN-95 mask the last day and was glad to have it.
I'm not trying to sway anyone one way or the other, just trying to provide a realistic preview of what you might experience when you are there. It was a bit of a shock to the system for us as we haven't really been around people much since March. Overall we had a good trip, but it was a bit more stressful just being constantly concerned about distancing from others. It scratched a big itch for us and it was great to be "home" but we will cancel our March trip and rebook for a later date when we are less worried about being around crowds.