I've been using Solus as a daily driver now for ~8 month.
It has a pretty quick pace in term of continued development, and it works great. There were some issues lately, but they always got the fixes to the repos within max a week, sometimes just a day. That's pretty fast for a curated rolling release distro.
- lightning fast. Never seen a distro being that fast in booting or as responsive while being on the desktop.
- Pretty good software selection, personally I'm not missing anything.
- Devs are very responsive.
- The build system. It takes some time to get used to, but once you understand how it works it's great.
- Very stable.
- They make sane choices (in example: rather downgrade GCC to 6.4 than hitting performance just to use GCC7.
- The package inclusion policy is flawed for some corner cases. In example: no release for X month/years does not always make sense, in example for fonts.
- They're still a very small team. Compared to in example Archlinux, it often takes them longer to tackle issues.
Overall, what impresses me most is how fast the distro is moving forward. If they continue like that, I'm sure they'll find their place in the top-tier of distros one day, but I do not feel they're quite there yet.