Ulvenwald Mysteries is just one word away from
being a self-sustaining loop (that word, of
course, being "nontoken"). However, in the
context of Shadows over Innistrad, extra Clues
are definitely always a good thing, and extra
tokens are a good thing too. Controlling one of
these will make combat quite uncomfortable for
opponents, and probably make them reassess a lot
of their blocking decisions.
Another point of note: the concept of an action
like investigate seems to be opening the way for
designers to, at long last, make some sort of
follow-up to Steamflogger Boss. Watch this space
. . .
Somewhere in here, there's an infinite combo
waiting to happen. Ulvenwald Mysteries can turn
every creature death into an extra card, and
every one of those cards into an extra token,
but it's a slow process. This isn't Fecundity
we're dealing with here, folks. All the same, in
a slow deck with a decent amount of creatures,
this can help get you through the slow turns by
giving you a way to use excess mana and a way to
dig for what you need or to keep your hand
stocked and keep the pressure up after your
opponent has exhausted their resources.