Well, I just got these two aircraft (I already had the 550/700 for around 2 months) and just completed a flight in an Air Canada Express CRJ-900.
It works really well overall for me. I like the extra range and passenger capacity. The 900 and 1000 also seems to handle a bit better, especially on landing. For me, the 550/700 likes to float a bit, but the 900/1000 is much better in this regard. Aerosoft has yet again done a really good job!