I should add that I work in the industry and have seen, literally, thousands and thousands of boats with plastic tanks over the years. The only issues that I can remember seeing are owner-caused issues... such as drilling a hole for mounting a rope hanger into a bulkhead, not realizing the tank was on the immediate other side of the bulkhead, and drilling too far.
That's not to say that they are impervious to issues, but they are definitely much fewer and far between than aluminum.
Yes, ethanol is a non-issue with the tank. Less chance for condensation to build up, too.