You are right, the Hurri is a simple fighter and Nils did an awesome job, no doubt. I have it and I love it. The best Warbird available for XP. However, when I talk about systems depth and about warbirds I mainly talk about the engine simulation. Also here the Hurri is not bad, but I am talking about the engine and its systems being strongly dependent on outside air conditions (temperature, density etc.), the aircraft geometry itself and pilot operation. Problems with oil temp or CHT temperatures, if the pilot does not keep the engine within limits and cool. Realistic engine start-up with a cranking engine which fires not necessarily immediately, depending on outside conditions and pilot operation. You will have wear on the engine and its parts and finally that all systems "communicate" with each other, just like in the real deal. A realistic hydraulic, fuel and electrical system. You get the picture. Again, Nils did a fantastic job, but I haven't seen what I wrote above in depth on any XP warbird. Also authentic and realistic sound is very important. It is a huge player when it comes to immersion and the feeling of being in the aircraft. Sounds should be recorded from the real aicraft when possible and not just the engine sounds. XP has its limitations when it comes to sound, but this can be solved or at least improved by using OpenAL and Nils is doing that now for his BK-117. Also the BK-117 seems to have a lot of system depths, but I can not talk about it since I am no helicopter pilot, really. I just saw the videos of the BK-117 and they look awesome, especially with the new sound engine.