I think what makes me feel great about having the D800, and I can equate this to guitars also, is that you know you have in your hands the absolute best tool that will maximize your performance. That challenges you. You can't look at a poor photo and say "Well, maybe if I had this camera or this lens, it would have turned out better." No! It would have turned out better if you knew what you were doing; if you were more creative; if you had taken the time to study the subject more.
I also play the guitar, acoustic only, and have guitars that cost much more than the D800 (see ARK New Era Guitars) and when I pick them up to play they not only feel and sound great, but I know that the burden is entirely on me to bring out the best in them. Any inadequacy is entirely my inadequacy. There is something great about eliminating all excuses.