I am also a 7D shooter and will hang on to it as my second body. If it helps, I am going for the Mark III.
My thoughts - I love the 7D, but some of my photography is low light - sunsets; sunrises; early dawn; moving cloud or stars; snow storms; or night time events. I have to ISO up to keep the tight exposure. And noise is an issue - and its most noticeable after I recently invested in a NEC Wide-Gamut IPS Monitor and can zoom to pixel level - blah! DXo7, NIK, LR, and other software does a nice cleanup but you will lose detail -and - it is good to have the best source possible at the top of your workflow. After swimming with photographers with great lower-noise FF's such as the Mark II, I hear them and I must make the jump.
My issue with the D800 is that the pixel pitch is similar to the 7D (as a NR rant somehow made that a plus?) and while its a better Sony Sensor --- I just do not want to end up with a FF version of 7D noise. At 100, beautiful. At 3200? If I was shooting studio or architecture on bright sunny days, the D800 has its merits; oddly similar merits to the 7D at crop size.
For me - I want to work on the shot - and if I need to bump the ISO to freeze the clouds/stars or get that stage performer in sharp focus or whatever I am doing - I want that headroom. And on the post I want to focus on the artistiy; and not spend hours cleaning the crap out of an early dawn sky - I want that win.
Thats my neurosis coming out of the 7D mill.
There's significant difference in sharpness and other qualities when you get into the "L" territory (or their Nikon counterparts), and personally I think the grade of the lens is more important than the "muscles" of the different camera bodies.
Absolutely. I recently rented the 135 f/2 and wow!!! New camera. I now have the 70-200 f/2.8 IS II and beautiful + the room 4-stop IS gives you. Got to sell my EF-S 10-22 glass and am in a tough debate on my next UWA. I have also tried bad glass - yech! Definitely good glass is most important!