I've had a number of cheapies, but I usually can get them to work pretty well, with a pick up change and some tweaking.
Some, however, are just 'snake-bit' as we say out west.
Right now I have a Strat-style guitar that I've been throwing money at, off and on, for years. It just sounds bad/dead/dull, with any pickups and will not hold tune long enough for you to let go of the tuner button. The bad thing is, every part in it is name brand and every adjustment that can be made, has been made 6 times. Its haunted.