Show and Tell for instants

So I'm not doing this not so much as an attempt to design an awesome card, but as a thought experiment about why [[Show and Tell]] is so good. I actually think the resulting card is, surprisingly, not particularly powerful. I guess I want to know if I'm wrong about that.

Science Fair 1RR

Sorcery

Starting with you, each player may cast an instant from his or her hand without paying its mana cost.

There are three big deviations from being a "spells" version of Show and Tell. First, it doesn't cast sorceries, while S&T will play most permanents. That's one of the two biggest limitations of the card because what's available to "cheat" onto the stack among instants isn't as game-ending as the best creatures.

Second, it follows cards like [[Genesis]] in having each player choose what to play sequentially. That's better for player understanding because S&T can be pretty weird, sometimes. With spells, that problem's even worse because there are targeting issues. That's actually the other big power limitation of this design -- whatever you cast with Science Fair, your opponent can counter for free if they have any counter spells. It's similar to the way Karakas limits S&T, except that the answers are more absolute and ubiquitous.

Third is the mana cost. It's red, and has an extra color symbol in the cost. That means the decks that may most want to use it -- an [[Omniscience]]-style deck with this as the centerpiece or a storm deck using it as a wierd ritual -- will have a harder time casting it than if it were blue. Additionally, it can't be played off a Sol Land plus one normal land or a [[Lotus Petal]], limiting the speed of any combo deck designed to abuse it.

Having looked through the highest cmc instants, I earnestly believe that this card is not overwhelmingly powerful. The best things you can do with it are to hit for lots of damage or high life swings, maybe while killing creatures or destroying a couple lands as well. An alternative strategy would be to use something like [[Firemind's Foresight]] or [[Dragonlord's Prerogative]], but that would be a two-card combo just to assemble other combo pieces. In either case, it's still particularly weak to counter spells, more than perhaps any other combo card, and aggro decks and other combo decks can probably race it because nothing it does ends the game or seizes absolute control of it immediately.