I've been ok with Europcar over the years. I book with the consolidator Autoeurope who have always hooked me up with Europcar. that said, I've never had any claims or dealt with anything that required customer service.
I always check the car quite well before taking it as they often have a narky attitude when I deny their CDW coverage. If there are a few scratches and the attendant tells me not to worry, I'll make sure they write it in to avoid any bull****e when I return it.