Originally Posted by Psimet2001

My general thoughts (ATMO)

One of the best groups that Shimano ever made - 7800.
I believe that 9000 mechanical is possibly even better...time will tell.
Di2 - is the best style of group in the world for enthusiasts. I keep running into a lot of racers who do not like it and have switched back to cable systems. As a mechanic - I don't care - either is easy to work on, but I always have extra cables in my tool box - not extra wires

SRAM - High caliber stuff at low/reasonable (wholesale) prices. If I am building a bike I don't even think - it will have SRAM on it. Shimano is too pricey on the wholesale side and they just moved everything back in house distribution wise. I can call 5 places and have SRAM parts the next day.
Just about everyone we race with or around has SRAM. Easy for parts and fixing/swapping when needed.
SRAM support at events is the best.

Campagnolo - IMHO - the best absolute mechanical systems available. Really well done all around and great stuff to have in your hands.
Not practical for me or any of my uses. Every year I have 1 or 2 racers on Campy and it's always a huge PITA. I can call the same 5 places and get parts, but stock and prices are prohibitive.
I have watched the local racing community slowly go from about 20-30% Campy before SRAM came out to road to being roughly 1-3% now.
I still get a steady stream of Campy orders but they are small in number.