I just bought the Keylab Producer Pack and have been playing around in Bitwig Studio on Windows 7 x64.
I noticed when I do the drag and drop audio clips from Spark2 VST into Bitwig 1.0.15 it shows the "can't drag" icon, unless I move my mouse around the screen for several seconds and then it lets me drop the clip, or sometimes it crashes saying it can't open the file and I have to manually kill the plugin process. It doesn't seem to have this issue for drag and drop of midi but then I can't use Spark's FX features.
Everything works flawlessly in Reaper, but this is a bit of a workflow killer for switching to Bitwig.