Comparing prices for the same wine, I think Buon Vino is pretty average.
In terms of VFM, my experience of BV, and natural wines in general for that matter, is that they are either very appealing, or very unappealing - a greater range than most other wines. But the duds are cheaper than Burgundy duds ;). And I think it is fun to explore.
My last very postive experience from BV was a £14.50 wine - a Campania IGT Aglianico from Il Cancelliere. I returned to get half a case of that a couple of months ago. Claimed to be natural.