Originally Posted by John E

I disagree about the "extra cog" being essentially unneeded. I can do most of what I want with a 2x6 setup, but 2x7 or 3x6 works out better for me, with good range and no gaps.

You are right about the benefit of an 8-speed cassette. My mountain bike started 3x6, was evidently upgraded to 3x7 by the first owner, and I have since upgraded to a 3x8 cassette, which gives me a delightful set of gears spanning almost a 4:1 range (26 to 100 gear-inches), with 6-7 percent progression most of the way up.