Dual rear blinkies? What's the rationale? Two points --> better depth perception for drivers or just twice the rearward light? When I'm driving behind a cyclist with even a basic LED blinky, I NEVER have any problem seeing him, even in pitch dark. They're visible for miles.
What all can you fit in the small seat bag? Can you get a tube & basic tools in there?
How do you carry your commuting luggage? Messenger bag?
Last year I met this rider named Dave, who commutes between Anaheim and Long Beach, on major urban streets. He has been using duel lights for a while. His argument has really been about maximum visibilty. After that, I started to. It seems like every knucklehead in Southern California is either on a cell phone, texting or distracted in a hundred different ways. I often ride at night and am pretty paranoid about getting hit. I feel like the alternating stobes will draw a drivers attention toward me, therfore acknowledgement I exist as a human being. I'm not dead yet, so I guess they're working ok.
About the saddle bag, I carry a multi tool, patch kit, tire levers, a shop towel and $5 in $1's. My ride mostly follows a bus route so if I flat out mid-ride, I'll just take public transit. If I flat out at work or school, I can spend the time and fix it there.
I carry everything in a backpack. I've tried shoulder bags, they slip around to much. I have a set of panniers but removing them to carry stuff around during the day has not proven to be practical. I've worked to cut weight down, my best idea has just been to just leave a lock chained to the rack at school and one at work. That helped alot.
As for the discs, no problem at all. They are a little finicky to set up and to keep tuned but their stoping ability is second to none.