6'1" 145 lbs here. Extreme ectomorph. Used to be much skinnier than this, but I bulked up over the past 2-3 years. I used to be one of those emaciated skinny types where you'd see me and the first thing you'd think is, "damn, he's fucking skinny." My ideal weight is around 175 lbs but that would take me an eternity. I think I'd be content at around 160 lbs.
I'm still skinny in the sense of the word, but I have much more muscle mass and definition. Went in for a health check up bout a month ago and they said I have low levels of bad cholesterol, ideal levels of good cholesterol, excellent heart rate, and 4.5% BF. The nurse was flabbergasted at the BF percentage. She said I should keep doing what I'm doing because I'm in excellent shape.