There are 4 cases:
If you open with it you can only net trash one card with it (sure, you can also quasi-trash 2 Estates and gain a Copper).
After your deck has some good cards it becomes really good: trash 2 you want, gain 1 you want.
Respectively a bit late: trash 1 you want, 1 you don't want and gain a copy of the best of the 3.
It becomes worse when you have to trash 2 good cards and gain a copy of the best.
So overall better than Lookout but terminal. Should probably be OK at $3 or $4.