My biggest complaint is that their App store isn't just F-Droid, and their APKs are often out of date by 1-2 weeks. My biggest compliment (besides everything just working to the point I could recommend it to a relative), is that they are active and engaged in their community, regularly reading their forum, soliciting feedback, and posting weekly updates.
https://community.e.foundation/t/week-41-development-and-tes...
It's pretty good most of the time. It will not satisfy people who want/need a truly "hardened" device, but if you are just a normal person who wants to feed less data to the ad-tech monsters, then it works well.
The default /e/ app store has both FLOSS apps from F-Droid and free-as-in-beer proprietary apps mirrored from Google Play store. Whether an individual app works well or not depends on how tightly coupled it is to Google Play Services
I used it without their cloud services. Some of the pre-installed apps cannot be removed (like email, pdf readers) which is slightly annoying. They have their own launcher/desktop but it's not that good, it even crashes time to time.
Last time I checked, it was not super transparent which non-FOSS store they used.
Overall I think the experience with LineageOS is better but /e/ comes with MicroG so it's practical if you need a few proprietary apps.
I'm pretty sure that's deliberately opaque because mirroring APKs from Play store breaks some ToS somewhere and they don't want everyone getting their Google accounts banned.