Challenging to an extreme if you don't use a blind. Can't hunt from a stand as with a deer--some deer don't look up all that much, and most of the ones that do don't "pay attention" all of the time, so you can eventually draw. Or, if don't get an opportunity on one, most likely will on the next.
Turkeys do look up as much as anywhere else since danger does come from above, and from what I can recall they have a bigger cone of vision than a deer, so much harder to ever be out of their vision to draw. Finally, deer may come in singly, or just a couple whereas turkeys frequently come in multiples, so more eyes to see any movement.
OTOH, I think they're dumber than deer--once a deer decides something is suspicious, it doesn't seem to "let go", and also has more memory retention for next time. With turkeys, sometimes it seems like they have a short-time memory loop, if something seemly suspicious doesn't seem to be dangerous they forget it and go back into a normal routine (that's not to put down an old bird, who are as smart and wiley as anything--comment applies more to my experience with average animals).
With a blind, I think they're easier than deer, not as suspicious--have to do a better job of brushing in with deer.