Here's my take on the 300. I have no experience with the 600 series.
The Good: The 300 is a good airplane. If the 300XR (or whatever it will be called) has what it is rumored to have, that will be an outstanding airplane. DOC's are great. Cabin is Great. Very popular on the charter market. Very simple, low workload airplane. Range, Speed, cruise altitude, and runway numbers are all very good.
The Bad: Bombardier support sucks, but seems to be improving slightly. Taking the 300 to Europe on the tracks is a bad idea, not enough redundancy for my taste. In fairness, it was never designed for that. Be careful of high BOW's. Our max payload, with full fuel, is less than 400lbs. East to West trans-cons with +4 pax can be a problem. We had a scenario not long ago where BUF-SFO with 5 pax was pretty close. They dont call it the "reset jet" for nothing. You will occasionally have to power down and unplug batteries to clear erroneous CAS messages. Autopilot is not smooth and doesnt handle turbulence very well. Pretty Mickey Mouse for a +$20M jet. We had some reliability problems initially but have seen good improvement as we worked the bugs out. Its not a great hand flying airplane. Feels like the controls are attached via bungee cords.
I (and all of our other pilots) still prefer our G-IV. But, then, were not paying the fuel bill.
All in all, a good plane. Not great, yet.
