There's not much more to say here than I think this card is a nice way for Control to snag an early engine card from these decks, and then have room to Stock Up or Consult the Star Charts on the following turn
Coming out of last week, the top decks included 2 copies of Amulet Bloom, a resurgent Jund build, a fairly stock Merfolk deck, Grixis Twin and two copies of R/G Tron, with the latter taking down the tournament
For those that want the lengthier version of the story on how Vehicles came to be, here's a link to the article that talks about it
Like most Magic: The Gathering cards, the value of Arcane Signet depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Secret Lair Drop)
Ah yes, proliferating
Only 1 mana, but sorcery speed