Pipe insulation can be used for both purposes. As I am on well water, and wanted to avoid the condensation issue within walls and the floor system, I had the cold pipes insulated. I didn't insulate the hot pipes, and perhaps I should have, as that would be for heat conservation, generally a good thing. It would keep hot water in the pipes hotter longer between intermittent uses at a fixture. However, the piping is PEX, with "home run" dedicated lines to the fixtures, so the delay in getting hot water back was not of as much interest to me.

Insulating the hot water distribution plumbing results in a modestly lower hot water heating energy, since you abandon less heat between intermittent draws to dissipate into the surrounding space. Using 5/8" or 3/4" walled (~R4-R5) closed cell pipe insulation is preferable than the 3/8" walled (~ R2) stuff typically available at box stores, or the even thinner stuff designed only for limiting condensation potential. It will deliver higher initial water temps (more likely to be used, than purged) out of the taps even a half hour after the previous hot water draw than the R2 stuff (but even R2 is WAY better than nothing.) See:

http://www.leaningpinesoftware.com/hot_water_pipes_pipe_cooling.shtml

http://www.leaningpinesoftware.com/hot_water_pipes.shtml

For all but the lowest-utility cost areas there's even a sub-2 year payback on water heating energy costs, if done as a DIY.

Thanks for the info and clarifications.
This sums it up good. Will go ahead and insulate.
Cheers.

I also made a research on this thread and I have to share this little information that I got.

Reduce running water syndrome. Keeping the water that's in the pipes at the desired temperature puts the kaibosh on running the water til it warms up, or cools down.

An alarming amount of your water is probably going directly from faucet to drain, with no stops in between, just waiting for it to arrive at the perfect temperature. Once you've finished insulating, add water savers to your faucets for more water savings.