Anyone try the Edelbrock VRS-4250 Carb yet?

I don't know what I don't know regarding carbs. There have been comments that this carb might not be best for a street application because of tune difficulty and stability and I'm wondering what feature unique to the VRS (or other carb) would cause this? I can understand having more dials to twiddle causing you to get lost in the tune, but once optimized the engine combo, what would cause this one to fall out of tune while an older Holley wouldn't? It's not like the bleed orifices or jets change diameter over time. Is there a feature or circuit added that makes it susceptible to atmospheric changes?