mercury vapor lamps are basicaly floros, floros are filled with mercury vapor and coated for spectrum accordingly, the mv lamps run quite cool, after posting earlier I dropped my lights to 6" and when I got back from work, obiously no problems. I found during the course of my last grow, I was able to get the plants no closer than 1" from them(yep one inch, 2 intake fans, three fans for movement and a ceiling exhaust, even buds suffered no ill effect to being that close to the bulb, I will update this thread often to log this grow. tomorrow I'll post pics of the setup... probably....
As for efficiency, yeah they do suck, but my dual-headed sparc ultra10 uses way more juice, so I use my laptop more and installed those "12 leftover cfls" and actually made up for the cost of running my whole set-up, plus some.

What a rant... cough.. cough...