I had a discussion with a friend recently and during that discussion, one comment was "Fitted sheets are really both the best and the worst", of course referencing them as awesome when put on a mattress and the worst when you're trying to fold them.
What else do we have that would qualify for being awesome, but also the worst in a different context?
Things with wireless power (small vacuum) are terrific and convenient until they run out of battery or stop holding a significant charge, at which point they become embarrassing
A broom is always a broom
I love the fact you call them embarrassing instead of useless.