I have uploaded everything important to Kobo and I can be pretty sure the formatting is acceptable to terrible.
I started with docs. It seemed fine. Then it wasn't. Most of the rest were downloaded mobis and they're not perfect either. They look fine on my Kindle.
I have Sweet Tarts for free and I think Her Cold Kiss or maybe Murder Is Exhausting. I like the flexibility.
And I know that there have been people who put something on Smashwords for free forever and did really well once Amazon price matched (so reluctantly I'm sure).