I've been running firefox on my laptop for the last year, with Chrome on my desktop, as a way to head-to-head them. For folks contemplating the switch, it hasn't been bad at all. Some better, some worse, but overall I rarely notice major differences except for a very small handful of sites that won't work with FF.
And I still have all of my uBlock origin happiness. :)
Be sure to use "Report broken site" in the main menu on that handful of sites. Often there are things folks can do to fix it for you, if many people are running into it - but only if it's known.
My biggest complaints with my switch is 1) no Chromecast functionality on Youtube and many other supported video platforms, 2) Very minimal page/text translation services (Arabic is missing), and 3) no search or translate from image (google lens) which I have gotten pretty used to. Oh and also, seeking videos is weird on FF, the mouse goes way past the scrubber when fast-forwarding or rewinding, just seems weird..
Add-on replacements:
- Linguist for translations.
- Search by Image for reverse image search (there are others that just use Google Lens directly, but I use this one).
Cast is a bit more cumbersome. There is fx_cast on GitHub, but it requires a companion app. Firefox seems to want to add cast based on a flag you used to be able to enable, but I'm guessing there are some restrictions from Google's end they ran into.
I can't login to the work-paid-for version of Microsoft Copilot with Firefox, for some reason. I've had one or two others - I think they were internal CMU website tools. And even more niche: My kids took a ski lesson last year at Snowbird and the website with their report card rejected anything that didn't identify as Chrome. It _worked_ with mobile FF, but it popped up a "YOU SHOULD USE CHROME" banner and wouldn't let me past.
So, small stuff. Maybe Copilot isn't working because of ublock, though.
In my experience if something isn't working in firefox, it's more likely that it's firefox antitracking setting much more often than ublock. You might try turning that off first.
I've been daily driving Firefox for several years. Everything I use on a daily basis works fine on FF, but every now and then you come across some random site that doesn't load or loads poorly.
Why? I can just temporarily launch Chrome if I need to join a meeting. There's no need to have MSware running in the background 24/7 doing god knows what.
Expedia doesn't render properly in Firefox - some of the sections are missing, but it's not immediately obvious what is missing. It took me a while to figure out why my wife kept having problems with that site, and I had to move her to Chrome to allow her to use it.
I continue to use Firefox because I know when to suspect a website problem might be the browser, but she doesn't have the ability to analyze a situation like this. I have this conundrum with other family members that I support. I want them to use Firefox, but I hate to have them run into an issue because of the browser I recommended.
Bizzarely, Microsoft Word on web seems to be the only thing I've encountered which has FireFox problems, specifically it'll periodically "save" the document I'm typing and then delete the last sentence or two that I changed while it was saving. I think it's some kind of broken state management on the MS side (leave it to MS). That's the only site I've used though, and I've been a daily driver of FF for 10 years.
Sticky desktop notifications don’t work on macOS on FF, which means event notifications from calendar apps disappear within a few seconds, leaving no time to snooze them or act on them in any other way. Queue missed meetings.
I subscribed to SlingTV a little over a year ago and it did not support Firefox, even with all the DRM enabled. Although that's a problem I blame on SlingTV, not Firefox. It was a known issue which they refused to address. I've since ended my subscription with them.
IIRC, there was also a time when Netflix did not support its highest streaming quality on Firefox. I'm not sure if that's still the case since I also ended my Netflix subscription.
Otherwise I cannot think of any major site which is not supported on Firefox. Outside my employer's fragile intranet, I can't think of any sites which do not support Firefox.
And I still have all of my uBlock origin happiness. :)