I think that when you're mining and you want to mine just one block so you hold shift that it should mine a little bit faster (with more power) because you are concentrating your efforts on a single spot instead of a larger area. I'm not thinking an extreme amount, maybe around +25% power or -25% of the number of swings. I think it would be a nice little variance in mining and gives a little bit of benefit to mining single blocks because sometimes you need to do it to a few blocks together. Tell me what you think. ~Cire44Wolf
I quite agree, concentrated mining should be faster since you're working on one square rather than many at a time. Convenient for random ore chunks stuck somewhere.