You are welcome to come down and fly the ixeg 733 in my sim that uses all real parts as you are not that far away. As for VNAV, i had the privilege of having a real 737 pilot over a few times and we shook down the VNAV issue. Here is the reality, is it perfect, no ( neither is the real plane) is it usable, YES! If you build a proper route and hand build a viable descent, thet makes sense for energy management. it works! We flew a few LNAV VNAV flights and once we figured out what it needed, it accomplished it flawlessly. The problem is 2 fold, hit or miss nav data and ixeg's method of interpreting that sometimes screwy data. 2nd is the very very complex calculations of drag, speed, weight, time, distance, etc isn't perfect and you have to help it out. I mean come on, not to brag but if I can calculate in my head a manual VS descent that stays on profile, any of you can do it as well. Just apply it to the descent in vnav by verifying waypoints and altitudes and airspeed required. Any other words, by the smarter human and fly the plane and make it do what you know is correct.