The only downside to
Reality Shift, is realizing that you've been getting your ass kicked by a
mountain the whole game.
Damn near every deck has more non-creature cards than creature cards, so
odds are, your opponents are going to manifest a land.
Reality Shift is less risky than
Chaos Warp, and many people (myself included) use
chaos warp all the time.
Your deck is actually really well made, especially considering the low cost. You have enough card draw, but in a
counterspell deck, more never hurts. Remember, you're going to be countering the spells of 3 different players, so you need to be able to draw into your counterspells. You already have the good stuff (
Rhystic Study,
Opt,
Ponder,
Preordain), so the only things I can suggest are
Mystic Remora, and maybe
Azami, Lady of Scrolls. You have a decent number of wizards, so she'll give you lots of card draw, but 5 mana is a lot.
You also have a good number of counterspells.
Dream Fracture and
Swan Song are the only ones that are missing.
Finally, I don't know if you've noticed this, but you have an infinite combo waiting to happen. Imprint
Isochron Scepter with
Dramatic Reversal, and then have some artifacts that tap for mana (Say,
Sol Ring and
Sky Diamond), to generate infinte mana.