I started on the bigger tona, 02 955i, first bike I ever owned, and only bike I had ridden except the Bandit 250 at the MSF course.
No wrecks 18 months or so later and 11k miles. I commute daily on it, and do play on weekends every chance I get. For those who say "You loose out so much on the fine control by starting on a big bike" I say, those people are flat out wrong.
You learn MORE fine control because you have to, and you learn it faster.
I can't warn you enough, SMOOTH inputs, SMOOTH throttle roll on, SMOOTH braking. Be smooth, be smart, watch ALL cars near you, and do some stop/start drills and shifting practice.
Don't be afraid of the power, but do respect that the D675 will absolutely light up the back tire in 1/2 gears leaned over if you snap the throttle to WOT, in a corner so take it a bit at a time and dont try to be a racer right out the gate.
Three things the MSF wont teach you about starting off on a sportbike:
1) If the rear tire starts to spin, in a corner or straight, dont back out of the throttle right away. SLIGHTLY close it, like the smallest increment you can or just hold it in place and dont try to correct the slide, the bike will right itself.
2) Power wheelies are FUN, but to avoid them and maintain control get in the habbit of leaning far forward in 1st and 2nd when going WOT. Some bike will still stand up even leaning so play with high RPM in 1st gear carefully, you should probably avoid over 10k RPM in 1st for at least the first couple days
3) That 70/30 brake split front/rear thing is for a CRUISER. Under 100% max braking effort on the D675, your rear tire will be in the air not able to help you stop, and by letting the back tire keep rotating your helping stability while its in the air. The only times you need the rear brake on a modern sportbike are: Wet conditions, Trailbrakeing for stability in corners, and using it to help parking lot stability.
TL/DR: Buy it, but be careful of the power, and respect that its WILL hurt you if you let your EGO take over.