Well unreliable might not be the best word to use... but I do believe they are not very powerful,... or efficient... I just don't trust it in fuel critical situations. Happy enough to run off it only in good areas, straight and level, normal cruise flight etc. But if anything coughs the fuel pump goes on at the same time the nose gets pushed over...
It is a long way for that little pneumatic pump to draw fuel, especially with the outlet on the bottom tank. I was considering moving mine lower as it would push fuel better than pull it, I understand. (Nope... think I will stay on the bottom rather than rig a transfer to the top tank.)