I have to wonder what kind of games other have in 3x...
I got scry a little while ago. Oh boy, I said! I can use this horribly broken spell and ruin all my DMs plots! Bwahaha!
Not so much.
First, we rarely had more than a name for an enemy. We certainly didn't have their hair or know them well.
Second, any enemy worth scrying on usually has a will save from hell.
Third, any enemy worth scrying on either WAS a wizard, HAD a wizard, or was living somewhere BUILT by a wizard, and so was scryguarded out the wazzoo.
Fourth, nine times out of ten, we don't even know we HAVE an enemy until he launches his surprise attack when we're scattered all over town dealing with our assorted personal plot threads.
Basically, I have never managed to get a "live" scry -- that is, during actual game play -- which was remotely useful. During downtime bluebooking, I've said "I will be doing A, B, and C to try to figure out Foozle's defenses", and sometimes get something useful out of it, but since that's so much up to DM discretion, I could have just as easily said "I'm doing library research/gather information/whatever" and gotten the same information.
But to keep this on topic....
Either the DM *should* use scrying as the "Gilligan's Island Radio" -- you always tune in just in time to get the plot relevant information you need (which is fine) -- or there should be some way to be "smart" and make your small window of opportunity useful. For example, Loremaster's Bargain or the other "Oracle" type rituals can be used to find out when the best time to scry is. You can probably come up with other ways to make sure you're doing it right -- perhaps bribe a henchman of the evil overlord to tell you when he meets with his spymaster, or something.
Basically, given the high cost and level of scrying in 4e, it should be part of the player/DM social contract that it be useful. (It might, for example guarantee one or two successes in a skill challenge.) If the DM really hates it as a plotbreaker, he can, of course, simply make sure the ritual is never learned by a PC, which I consider fully acceptable. The 4e DMG talks a lot about saying yes...saying NO is also a skill DMs need.