Please educate me on Hardpacks

[duckbill]

My vote is "Heck, yes!" for the harness on doubles. I find them VERY comfortable. Everybody has given the main points already: Self-contoured to the back while diving; Closer to the center of gravity while walking/standing (seemingly unimportant, but it is surprising how much difference it makes); Regulator closer to the back (important for double-hosers); Looks cool!
Your tanks will really stand out at the dive shop during air fills. Be prepared to answer questions.
I have not dived a single with a harness, so I can't give my opinion on that yet. That day is coming very soon. I have a cylinder picked out for a harness and plan to be ordering one very soon. I really like Healthways yellow. Maybe Allan has tried some yellow dye.