For me it's been Eastern and South Central MT.
I have utilized a lot of Block Management as well as State and federal land.
I have been told the hunting is at a real low for deer and antelope. We have had good success on 3 antelope hunts and 3 deer hunts in the last 6 yrs. So all I can say is, If this was bad, I can't wait for the good times.
Not huge deer and antelope so far for us, but not to bad either. We've experienced lots of opportunity and love the flexibility of the long season to work around other out of state hunts.
As far as terrain, I think it's been fairly mild where I've been, but I have crossed through and seen all levels of difficulty for sure.
No experience with elk in MT yet, hopefully soon, but I will definitely be back for deer and antelope and maybe someday lord willing, (If I live long enough to draw) Sheep.
I've been in the mud near the breaks, and my advice is to heed the warning on the mud. It's bad stuff!
MT has so many options for places to hunt, a guy/gal could spend a life time and not get to enjoy them all.
It's an awesome place IMO. Good luck on your hunts!