I know that Spaces doesn't use the Play engine, however my general concern is just with East West's quality. Their programmers don't seem to be particularly good at making software that works well. Also, their management seems to be in a bit of denial about that fact. They have claimed that certain things are impossible, that are in fact not such as being able to handle fast bounces.
However after trying Spaces I decided I had to have it. It may be completely un-expandable and have a very simplistic interface, but it just sounds amazing. Hopefully it will be less problematic than Play has been for me.
I really wish East-West would just go back to producing samples and such, and you somebody else's engine like Native Instruments. They are some excellent audio engineers, that just don't have programmers that are as good.