I live in North Florida and we regularly get "hard freezes" here, so I don't think running the pipes in the attic would be good in this area. Attic temps do not stay above 100 degrees F year round.
If you have copper pipe, changing to CPVC will help as it has about 2000X less thermal conductivity. It's much better than just insulating copper pipe. Of course, if you're trying to capture heat from the attic, you should probably run copper up there as the CPVC won't do you much good (CPVC should work if given a long time to heat-soak, but you won't get much while the water is flowing).
Also, changing to smaller pipes as has been mentioned will help because you will have less water to displace. A 3/4" CPVC pipe has 1.75 times the area (and therefore 1.75 times the volume for the same length run) as a 1/2" CPVC pipe. I think it makes sense to run the larger pipe for the main lines to reduce pressure loss, and the smaller pipe for the branches (where the flow needed will be lower) to reduce the volume in the pipe. CPVC is also cheap and easy to work with.
If you're going to be redoing the whole system, look at how you can run the pipes to reduce the overall length of the runs. This will help to reduce volume also.
Some people run a separate line from a manifold at the water heater to each faucet, allowing a smaller pipe (it doesn't have to provide as much flow as a line that feeds multiple faucets) and therefore faster time for hot water to arrive.
1/4" copper is not recommended for flows above 1 gpm, and 3/8" copper is not recommended for flows above 2 gpm.
http://www.copper.org/publications/p...e_handbook.pdf