The best part of grey spark by far would be its ease in use, it's simplicity makes you feel like your using something that can handle anything with relative confidence! That said I think they could have made some upgrades or features recently but i'm sure we'll see them soon enough if not already available through updates/upgrades? Don't hesitate when considering this product as there are so many things about how easy gray sparks interface works well together which saves time compared what other products require (also having more tools at hand).
It has really saved me alot over my previous attempts trying out different BI solutions such us QlikView etc..