I want to chime in and say I've been interested in flight sims since the late 80's when they started on PCs, and I've seen nothing that comes close to what Accusim is doing, in all that time.
Spectrum Holobyte's Falcon 4.0 maybe, but mainly in its depth of systems representation, certainly not in its flight modeling, and it was wonky across the board in everything it ambitiously tried to do.
I've purchased the Cub, the Jug and the Spitfire, with their expansion packs, and am similarly saving up my pennies now for the Warhawk and Mustang.
Each of these are worthy, unique, full-scale sims on their own, something no other flight simulation modeling effort I've ever seen has accomplished. FSX and X-Plane, as good as each is in its own way, are each a single system with tweaked variables.
It is the SOUND along with everything else that gives these sims so much flavor. I'm a musician at heart and therefore absolutely love being able to rely on my ears for detecting subtleties, and the work done in this area, both in sampling and modeling, is phenomenal.
Plus you've really pushed the envelope on how to use physics in 3D software. The games industry, for all its bluster, has been stuck in a rut of rag-doll physics and simplistic ballistics modeling for over a decade, even for the most sophisticated blockbusters out there (trust me; I know whereof I speak).
You've made a huge leap ahead of everyone with your efforts; massive congratulations!