In my most recent visit to Montana, I played the Diamond X course near Billings, MT.
The Diamond X course is a decent course design but it's the rugged terrain that makes it stand out.
I had a little trouble following the course -- not unusual with disc golf and my local courses are even worse -- but mostly mystifying is that I could normally find only one tee box for each hole but they varied between green, red and blue (the blues seemed to be up top, maybe there is a pattern I missed). Many of the first nine seemed to be red or greens and the course was pretty easy in that area, minus the up and down terrain and almost certain bad lies no matter how good your drive. That's not a complaint -- I loved the ruggedness of the course. I was out of breath a few times from climbing to my lie.
Besides the terrain the other difficulty with Diamond X is finding your disc. There are a lot of crevices and small places for it to land. On several holes a hard rock or a big hill makes it easy for it to roll; hole 5 for instance is an uphill hole and it's hard to see where your drive finishes. I played the hole twice and the second time I lost sight of my disc but sited a landmark only to hunt for 15 minutes because it rolled to a place I didn't suspect. For that reason -- hunting for discs on shots that were in no way errant -- I spent probably an extra 45 minutes on the course.
Diamond X Hole Nine is probably one of the most well-known holes in Montana and it was pretty cool but not as risky as I suspected. I thought I'd be playing toward the edge of the cliff but in fact you play away from it -- at least on the drive. Plus the drop off is only 12-15 feet, which I suspected before I played the course. No course designer is that sadistic.
You almost certainly won't be getting worse than a bogey, maybe a double rarely. I thought it might be a major lost-disc hole but it's not. This is cool, though. I don't think any hole should require you to be a pro just to keep your disc, or to save you from having to hunt down a hill or off a cliff for an hour to find it. Toss in the sandstone surrounding the basket and you'll be getting huge caroms and skips. I thought this was an adequate hard:fun ratio. I only found the green box, though, which was less than 200 feet and a pretty easy drive though I was really low and still hit the deuce. Watch below.
Up on top, starting on hole 10, there are two directions you can go. I went right and around the rim with mostly (all?) blue tee boxes. I had some trouble finding 10 and the length on 12 was way off (by 100 feet) but otherwise this is a fun, cool area of the course, with a great view.
Diamond X uses the terrain pretty well, including my favorite tee box of all time on Hole 14. I think a perfectly flat chunk of sandstone is an awesome teebox. Sandstone is probably the best surface because you get the grip of sandpaper and this box was flat. The company who can make a durable sandstone teebox to sell to courses wins.