When does one notice the weight of a bike? Lifting it, certainly, but more importantly when riding, climbing hills, wind.

I certainly don't go for light weight on my builds. I've never even weighed any of my bikes. I go for practicality and reliability. My taste tends towards mid-level components and frames. Too high end isn't my style, nor can I afford it. Low end is more trouble than it's worth for me. For this reason, my bikes tend to be relatively light weight for what they are, but more due to a result of the components and frames I choose rather than a conscious effort towards light weight.

There's an obvious difference when riding my cro-mo framed single speed vs. my 1973 Raleigh Sports when encountering things like hills or wind.