Awful, awful card. Out of all the TCU skill cards, this one ranks dead last. (EDIT: See below)
The problem is that 3 icon trigger. To get 3 icons off this card and therefore make it trump Unexpected Courage, you need to both have 8 cards in hand and then only commit Curiosity. This demotivates you from playing skill effects like Deduction or Eureka! as you drop an icon as soon as you commit any card alongside this one. If you only commit this card, it becomes 3 for 1 card, but if you want to commit anything else with 1 , you drop to 3 for 2 cards, which is abysmal for a skill card that only gives icons and has no other effects. To add insult to injury, with 8 cards in hand you probably do have something like Deduction or Eureka!, in which case had you run Perception instead, you'd still effectively get 3 for 1 card, but you'd also get the trigger of the other card you committed. Situational cards that you run for icons most of the time like Ghastly Revelation or Connect the Dots become worse as well, as again you're demotivated from using them when they're useless.
All of that was just analyzing this card for when you get the most value out of it- at 8 cards. This effect get so much worse once we take ourselves out of being at 8 cards. At 5 and 6, you really don't want to use this card with anything else, and if you have a particularly hard test to pass and need to commit your whole hand, be ready for this to drop to 1 icon. To add insult to injury, the icons it gives are the most common across Seeker cards: and . It's incredibly rare you'll ever need the flexibility of Curiosity being able to commit to either test when your hand is already that full.
That said, I can think of exactly one investigator who could use it. Minh Thi Phan needs skill cards, and she could run a heavy card draw strategy with Grisly Totem, Laboratory Assistant, Cryptic Research, Glimpse the Unthinkable, etc. all of which help Curiosity's stock go up. She can even run Able Bodied alongside it, which covers all 4 icons, and Minh isn't particularly item hungry either. Outside of that specific build though, you as someone with access to Seeker cards are spoiled for choice: Inquiring Mind might as well be 3 (and occasionally even better than that), Eureka! is crazy good card filtering, and Deduction is almost an autorun skill card in multiplayer for the tests it saves you. I would take all of those, Perception, Guts, and Unexpected Courage before I took this card.
Avoid. If it helps, you probably are not the cat.
EDIT: Well fast forward six months and already we have a way of making this card work. Dream Diary has an upgrade that depends on you having 8 cards in hand (it also gives you Essence of the Dream automatically every turn to facilitate this); Dream-Enhancing Serum helps you maintain duplicates, which is particularly great for Myriad cards; and A Glimmer of Hope can, on demand, help fulfill the condition as well. Again, this suite seems to point to Minh Thi Phan as the best candidate for such a build. I'd still say outside of such a build you should avoid Curiosity, but in this build it could be an absolute cornerstone, much like Cunning in a big money build. I'm happy the card might have found a place.