The Shadows Over Innistrad previews have started and I'm actually more interested in this set than other Magic sets. I still don't like double-faced cards but hey, at least I know what I'm annoyed at going in!
There is one card I've seen, however, that made me worry.
Pore Over The Pages.
Back in Urza's Block there was a mechanic in Blue that allowed spells to essentially be played for "free" by untapping lands equal to the casting cost of the spell. If the CC of spell was 5, then untap 5 lands, for example. Some of these spells were fair, like Rewind, but others, Frantic Search and Cloud of Faeries, were overpowered. Rare was the sweet spot hit-I'd say Treachery probably comes close but even that card is absolutely brutal. This might have worked out OK, except this was also the block that printed Tolarian Academy.
The lesson-one that Magic has had to repeatedly learn-is that giving free anything is extremely risky to gameplay, and giving free things to Blue is Very Bad, if you're interested in providing players with a metagame that is varied and interesting. Uzra's Block taught us that. So did Mirrodin. And then New Phyrexia. Then Khan's block. You know, in case the lesson didn't stick.
Now, if we had environments where lands didn't ever give people two mana, that might be one thing. But both Modern and Legacy are currently being heavily impacted by the Eldrazi enabler cards; lands that tap for two to give players a huge jumpstart on mana, allowing for heavily lopsided board states early on. There have been combo decks made from the common land cycle in Ravnica block, decks that have resulted in bannings.
I realize that Pore Over The Pages is not the same thing as Frantic Search. There are some very significant differences that I have to take into consideration: POTP only untaps two lands and is sorcery speed. These are not small changes!
But it still provides Blue with the opportunity to filter three cards and then either lay a new threat for up to four mana, or protect the current one with up to four mana, and that is potentially very, very unbalancing.
In Standard, a card like this won't make a significant splash but in every other format? I'd be keeping my eyes on it.