I guess I didn't fully understand your post then, I thought you meant that the Reyes algorithm is an "inferior estimation" and that it might be beneficial to add it to a renderer, but neither is the case. But it isn't an inferior estimation (just a different way of computing things) and you don't want to use the Reyes algorithm in practice as scenes either barely fit in memory or they don't fit in memory at all (and in that case you want your memory usage to be as efficient as possible to avoid reading from the disk as much as possible).