I generally like both. But not if the foreshadowing is too obvious so that it spoils everything - I prefer foreshadowing which I might only spot upon re-reading.

Agreed. I like twists as long as their not overly done or cliche' and foreshadowing can be good as long as it doesn't give away too much.

Also, the twist can't be so extreme that it really seems to come from nowhere or be out of character.

^True. I hate when that happens the story becomes weird and confusing and it really hurts the plot.