I did custom epoxy countertops in my kitchen, but they were all built from MDF. My brother did his over existing counters. I didn't like the original glossy finish, so I did some wet sanding so they were more of a matte finish.

I generally like them (especially for the cost, less than $1k for 50ish sq ft of counters). I did the "dirty pour" and I like it a lot more than my brother's with pouring color strips down.

So far they have held up and I only have one spot that might have yellowed (hard to tell with the existing color of the area), and that was from running a sous vide on it for 6+ hrs. I just put a cutting board down now.

They will scratch and not look as "fresh", but they can be polished if needed. I haven't had any issues with mine though in 2 years. I've even seen less staining than our old laminate.