I've been to Sturgis 11 times on various bikes. Quite the gathering. It has changed drastically since I first went in 92. Back then, most people rode their bikes. Today, most are trailered in behind pickups/SUV/fancy motorhomes. Back then, one could stay at ANY campground for $60 - $75 for the week. Now, motel 3 1/2's go for $300/nite 50 miles away. Today, the rub/yup crowd pays up to $900/week for "catered" tent camping at the Buffalo Chip. The Buffalo Chip campground gets 50000 people, nudity and public sex displays are common and its anything goes. What really slays me are the conditions at Buffalo Chip. They have the worst outhouses on the planet, last cleaned when Eisenhower was president. I think their outhouses are quite a bit like the mustard gas used in WWI. One may recover from being exposed to it, but is never quiet the same. Millions of those big black shithouse flies. Impassable mud when it rains, dust when its hot. Not a bit of shade. Quiet time is 3:42 am - 3:54 am on Tues & Thurs.
A visit to Buff Chips when they held a motorcycle auction (95) forever cured me of any desire to stay there.
While its true well over 85% of the bikes at Sturgis are Harleys, I had a blast there regardless of the marque of the bike I was on.
BMW has their demo fleet, as does Honda, Kawasaki, Yamaha, Victory, HD, Boss Hoss and maybe a couple others. I've taken demo rides on all the bikes but HD. None of the other manufacturers come even close to BMW, as the BMW folks give a talk on safety, operational details and having a fun ride. Kawasaki was (IMHO) probably the worst, as they talked down to you like little kids and set a bad tone.
Fantastic riding in the Black Hills. Spearfish Canyon. Custer State Park. Needles Highway. Vanocker Canyon. The Badlands. Devils Tower. Mount Rushmore. Deadwood. Keystone.
Have fun. I'm sure you will!