In the right go-wide deck, such as Elves or Goblins, you can easily get boosts in the +4/+4 to +5+5 range going, too, which are very hard to deal with
Your first win in Jumpstart will net you a rare card, with your second victory securing another
Creatures you begin to control later in the turn and permanents that become creatures later in the turn won't gain haste
Comet Storm, however, has a mana value of 2 in exile and can be flipped off cascade, but if you cast it, X always equals 0
Ahoy Mateys The seas are a dangerous place, and thats especially true on Ixalan
Also keep in mind that if you successfully import a deck, you may still need to make sure you've selected the proper format (if you import a Timeless deck but set it as a Standard deck, you'll get an Invalid Deck error message)