Not at all, I wouldn't recommend it on the road, but for drag racing its definitely worth it. You can hear the engine revs momentarily hit the limiter as i change gear.maybe a silly question, bu. does it hurt anything? i have a function in my current engine management to do this. never tried it but...
As long as you have a rev limiter and don't mis-shift, it can't do any harm to manually flatshift like this. I suppose it's quite harsh on the clutch, but nothing drastic.
Not familiar with Ecu controlled flat shifting, but I imagine that will allow you to control the RPM the engine goes to when you dip the clutch to change gear??
The Launch control feature on Nismotronic is pretty handy too.