I am a helicopter pilot..when I'm not out taking landscape photos to order!
I have flown professional photographers around the mountains of New Zealand for many years now. Guess it has been a speciality of mine, made all the more successful through my own knowledge and interest in high quality landscape imagery.
First of all, as mentioned previously, find yourself an experinced photography pilot. Secondly demand the door is removed, it is near impossible to capture good images through perspex without also capturing reflections, scrathes and squashed bugs!
Thirdly come well prepared with batteries etc. If possible bring spare camera bodies with varying lenses as changes lens etc in flight will cost you lost images and extra money in wasted flying time..and it aint cheap!
Fourthly I have found the vibration in the machine is not a huge issue if you are not in contact with door frames etc. Far more important than that is shutter speed and iso performance. Unless you are shooting in good light levels you MUST keep an eye on shutter speeds and increase iso to keep them fast. Therefore iso performance as it relates to noise etc is very important. I have found to produce sharp images from the heli platform you must keep shutters working faster than 320 ideally over 500. Careful with polarizers as they slow down shutters and produce uneven results on wider lenes. Fifthly make sure your pilot slows the machine down for critical shots. Not necessarily hovering as that can produce a more unstable platform but slow down as much as possible it helps with composition and image quality. Anyway good luck and have fun!