I've had a Black & Decker bump feed for close to 10 years now. Clean the shaft base every now and then and I've never, ever an had an issue with it. Which is surprising, as I'd never buy a Black & Decker power, hand tool. They are mostly junk. I certainly can't knock this trimmer though.
I can't imagine having to stop and replace short strings all the time. Maybe they are more durable though so you don't do it as often.
I can't speak for all units quality but I suspect that some people with issues on the tap & feed are probably treating them as smash and feed. I know that is what my neighbor's wife does. Poor trimmers over there do not last long.
