I would say that it really depends on the kind of orchestral writing that you’re doing, as well as the sample libraries that you’re using.
If you’re suing relatively dry samples, such as LASS, VSL or Sample Modeling, products like VSS and MIR help you create a cohesive traditional orchestral sound by not just panning but positioning instruments on the stage.
But…if you’re doing modern / hybrid type cues that sort of “classic” approach may not as important.
Would I use VSS if I was just writing a typical cue and adding “orchestral” instruments? Probably not.
If, on the other hand, you take orchestral writing fairly seriously, Something like VSS, MIR or SPAT, may be necessary.
VSS is the least expensive, and possibly most user friendly.