Hi,
Yes, I was using flexmonster and fusioncharts with 5.7 for an app that I built quite successfully.
Works really well and now with html5 support it should be even better.
Support suggested that I disable XML extention handling from the tomcat side of awareim, side effect of this is that it breaks REST. I haven't had much success late on Friday afternoon, but will try again Monday.
I suspect that its also the way AwareIM extensions work that cause issues with fusioncharts.