Count seems exceptional in curse-heavy junk games. Look at the following scenarios:
a) You draw Count with 3-4 junk cards (curses, estate, copper). Top-deck your one good card (or a Copper) and trash the rest. Or gain a Copper and trash them all.
b) You've bought a decent amount of terminal actions because your deck is bloated and want to see those actions more than once in a blue moon. One ends up in your hand with Count. Top-deck it and use Count however you want, while not wasting a play of your other terminal.
c) Your average card value is well less than $1 due to cursing or Swindler or alt VP gaining or whatever. Count's drawback of gaining a Copper now increases average value of deck, and you can use the benefit as you see fit.
d) You draw Count with treasure that's $3 shy of whatever power or VP card could help you out. Take the least painful drawback, and Count becomes your terminal Gold.
e) The bloatfest game is winding down, curses are gone, and one other cheap pile is almost gone, too. You're in VP-gaining mode, and lookie here: free Duchy gains until the cows come home! If you only have $2 left (for an Estate) with the other money in your hand, Count ends up being like a +$5 +Buy. And the drawback of gaining a Copper becomes even less significant if you may never see it again.
f) It's a Gardens game, in which case gaining Copper is a benefit, and gaining Duchy is awesome. Probably slows down end of game if the other player is not going Gardens though, since running out Duchy is hard. But in the mirror, Count rocks whenever you can afford it (adds 3 VP, 2 extra cards to your deck!)
In boards that are not massive slogs, I suspect Count's value drops significantly, but when your decks are filled with crap, you can count on Count.