I have a hunch that this will, in the end, be a massive win for large retailers vs. small ones. The task of figuring out how to calculate tax for all states is more or less the same amount of work regardless of size, which means for someone like Amazon it's more or less trivial, but for a mom-and-pop store it's a major hassle.
I suppose we should continue that state of affairs, because heaven forbid we hurt the mom-and-pop online stores... Which make up a tiny fraction of overall commerce, compared to physical mom-and-pop stores.