I got a similar impression: as presented, with players drawing them every round, and building their own decks from boosters, I don't like 'em, either as DM or player (even though I got enough free cards to build a perfectly good deck). They add an extra step to your turn, and drawing a card at the start of your turn can cause you to re-think the actions you'd been considering. If players use them seriously as presented, they slow the game down -more often, I see players simply forget to use them.Didn't see a poll option for my view:
-I haven't used them, and would not use them as designed, but could see creative uses for them by DMs (as bonus treasure, etc).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.