there are always security issues coming up, but generally it's so niche, and there's so many layers of shit that would have to be bypassed to get a successful exploit, especially if you use good hygiene within qubes (which is also necessary), that it's much less of a chance than any other operating system
but one thing i will say is it's fucking finnicky. The worst part is that sometimes something breaks or doesnt work as expected randomly, and i mean usually it's fixable but i did have to re-install one time and i never figured out why. It's also common to get corrupted (somehow? idk. some ppl had similar issues and the problem was the ability of the VM to make graphics? its fixable with knowledge) template vms by installing the wrong shit (calibre on debian, maybe whonix, lol).
I love it though, its super nice, it feels safe, it makes some things very easy (like having whonix vms is super cool), and i look forward to being forced to learn more i guess? Like SALT.
If you want totally stable and pretty secure, i'd go with a very minimal distro like void, and then do whatever security tweaking you'd usually do on linux. Qubes is less stable, has more moving parts, but it's honestly also pretty luxurious so i feel spoiled compared to a sparse, focused OS. It's way more n00b friendly as well, once you get past the first week and redo the install a couple times, and get you de/wm situation how you like it. It's pretty slick with i3. If someone just set me up a qubes computer and told me how to use it, it'd be way easier and nicer/cleaner than the average linux experience (even tho it's all linux still, lol). I'd definitely look into using it for a enterprise/org situation.
Protip: it eats battery super fast, so consider if you want a mobile situation or if you're gonna be plugged in.