Driving hard:
Drive the bike. If it worries you, buy an extended warrany. Shop around for the best warranty price, you don't have to get it where you bought the bike. There aren't enough of these bikes out there to really know what will break.
Shifting:
Here's a dyno run for a DN-01 although I question the review a bit; all their numbers are quite a bit slower than reported everywhere else. The reviewer is a full 1.5s off other 0-60 times. Maybe he didn't push the S button?
http://www.motorcyclistonline.com/roadtests/122_0910_aprilia_mana_850_vs_honda_dn_01/photo_24.html
You hit the torque peak by about 4500 RPM but the curve is very flat. There's not much if any advantage to winding the motor out higher. Clearly you're losing power past 5000 RPM.
Casually recalling what the bike does as you accelerate, it seems to go to an RPM and then stay there, changing the transmission ratio as you increase in speed. That makes sense with such a flat torque curve and is likely the fastest. The only advantage I see to manually shifting is that you can control the engine braking in the curves if you choose and of course it's fun and sounds good.