I do NOT have any flying time in the a/c, but I heard that there are (were?) CG issues with the early aircraft, as in it could not stay in CG with the fuel topped off and crew only. I understand that Gulfstream was working on expanding the CG envelope to fix this. It may already be fixed by now, I heard this about 6 months ago.

Also, the balanced field lengths can be lengthy, hot and high obviously makes that alot worse. That may or may not be a factor for your operation, since it seems like you are flying a C650, it may not be a problem.

While IAI still makes the aircraft, it is a Gulfstream, and they are well known for product support.

Hope this helps a little.