I've used the Floor malted Bohemian Dark malt in a lot of Czech lager recipes, I love the stuff. I recently made a Czech pale lager with 9 lbs Sekado Bohemian pilsner malt, and 1.5 lbs of Bohemian Dark malt and the color was exactly the same as Urquell. I did a single decoction with it, which adds a bit of color. It also added a nice maltiness that I really like.
You could use much higher percentages in a Munich Dunkel/Czech Amber or Dark Lager, I've done so and get nice melanoidin flavors from it. In my experience, the Weyermann floor malted pilsner malt comes out very pale even after decocting it, so adding some Bohemian dark malt will get you a richer, deeper color and malt character.