In contrast, I always thought that Deadwood was sort of a sheethole. Too much traffic there for the casino. Of course I have no use for casinos so maybe that skewed my assessment of the place, but if you like that sort of thing have at it.
Not really much to Sturgis either, but never really considered it a sheethole. Been to a lot of sheetholes before too, and Sturgis doesn't make my sheethole list. Too tell you the truth, I was let down the first time I went to Sturgis in 2011. Perhaps I was as all pumped up by watching shows on the Travel Channel leading up to it. To each his own though. The rally doesn't hold a candle to Mardi Gras, or even a tailgate party at LSU IMHO. This year it will probably be not nearly as crowded due to the scaled back events for the rally, so it would be the year to go there, tool around town, see some vendors, grab some chow, a t-shirt and maybe a bumper sticker.
The usual sight seeing points in the area would be well worth riding out to see as well. Many are already mentioned; Black Hills Harley (lots of vendors there), Devil's Tower, Mt. Rushmore, Crazy Horse, the Badlands, Spearfish Canyon, the various National Parks, etc. All beautiful riding.
Hope that you have a good ride. Let us know how it works out for you and what you think of the experience.