I've done the sums before dropping back to basic store & I'm way ahead in not having to pay fees. 

The difference in FVF is 0.95 %.  

I was paying Featured Store fee of $60 per month, 1500 free listings & then around $97-$100 for the extra monthly listings (I have over 3100 listings).  I now pay $25 per month store fee & the extra 0.95%FVF which doesn't come anywhere near the $135 per month I save in fees.

So yes, for me it was a good move, but everybody has to do their own sums based on sale numbers etc..