Does Isochron Scepter imprint work with spells that have X in their mana cost?

Isochron Scepter allows you to imprint an instant card with a mana cost of 2 or less. A card with X in its mana cost (such as Brainstorm... wait — an X instant like Desperate Ritual isn't X, but something like a hypothetical X instant) can be imprinted as long as its converted mana cost (now called mana value) is 2 or less. When calculating mana value for a card in hand or in the exile zone, X is treated as 0 (CR 202.3b), so an instant with a mana cost of {X} has a mana value of 0 and qualifies.

When you activate Isochron Scepter and create a copy of the imprinted card to cast, that copy is cast without paying its mana cost (CR 702.2c analog — specifically the Scepter's own text). For spells with X in their cost, if you're casting without paying the mana cost, you cannot choose a value for X other than 0, per CR 107.3b, which states that if you cast a spell without paying its mana cost and it has X in its cost, X must be 0.

This means the copy is cast with X = 0, which makes many X spells effectively useless in this context. For example, if you imprint Spark Spray (an instant with {R} — no X), that works fine. But if you somehow imprint an instant like Aether Tradewinds... a better example: imprinting Repeal ({X}{U}) — it has mana value 1 (X=0 + U=1), so it qualifies. When cast off the Scepter, X must be 0, so Repeal would only be able to return a mana value 0 permanent.

In summary: Yes, imprinting works if the card's mana value (with X=0) is 2 or less. But the practical use of the copy is severely limited because X will always be 0 when cast without paying the mana cost.