I haven't played DCS:BS for a while due to an installation of Win 7 RC and the awesome Arma 2, but I'm currently in process of reinstalling it. Can't wait. It just sucks that I have to reconfigure my X52 Pro, G25 pedals and Trackir once again - That will take hours :(
But DCS:BS is for me the best simulation of an aircraft made to date. Once you get comfortable with all the avionics, you become one with it. And multiplayer rocks!
As you say Flyby - It depends on the mission designers skills. Luckily you can download lots of great missions from this very site. I feel very immersed with this sim.