I've been pushing it on my clients when I do maintenance. Since I don't really do any marketing at all, I can't speak to that, but I've found most of the clients I approach about the idea seem warm to it. LEDs are no longer the unknown they were, so people already know the benefits of longer life and lower power. What they don't do the math on is the maintenance cost savings in the long run, as well as the hassle of having to change out the lamps...either themselves, or to have me out to do it. When clients entertain several times per year, and have to have me out to change out a 3-4 lamps every time, it gets old.
I don't do system relamping. I've been phasing it in, taking out a burned halogen, putting in a LED, then checking my voltages. Once I get to 2-3 LEDs on a run, it's often time to drop to a lower tap at the trannie so I don't end up frying the rest of the halogens. This way people arent throwing away good lamps, and aren't fronting the cost of lamping the system at once ("what do you mean changing out 45 bulbs will cost me $2,750?!?!). It's far easier to swallow in increments. And better job security.