... You're stuck with that color. And, they can be slippery if you don't have a no-skid surface.
I like the idea a lot. THey're maintenance-free. Try and get some 'references' from an installer that's had one for at least 2 years. Then ask them about how they like it. Other than that, picture rain, snow, 'darkness', etc., etc., on it and see if you'd still like it.
My best to ya and hope this helps.
PS: If you get one, get a few 'extra' bits of material for handrails, balisters, posts, etc., etc., in case you need to do repairs. This type of product, unlike PT products, go in and out of style. In 3 years, you may never see your style again!