Yes, everyone loves coming to my place. I make great coffee, too
I don't run CMH bulbs (they don't make them bigger than 400w at the moment), so I'm not talking from experience. But from what I've researched, most will run on a HPS ballast (you will need to double check before purchasing, obviously) and can be beneficial for both vegging and flowering, as they produce a wider spectrum of PAR (photosynthetically active radiation - light is radiation) which the plant can use.
The old style of thinking was MH in veg - when the plant needs more blue/green spectrum - and HPS in flower - when it needs more red/orange. Think about nature: in late spring/summer the sun is higher and the sky is bluer. In late autumn/winter, the sun is lower and sky is redder. That's how most flowering plants have evolved.
But plants still need all the colours of the rainbow to grow efficiently - just in different ratios at different times.
And that's why growers started adding metal halide lights to their HPS grows at a usual ratio of 2HPS to 1MH to add more blue/green spectrum. Ceramic metal halide bulbs are supposedly the best of both worlds.
I say "supposedly" because I only form concrete opinions when I try something myself! So I would love to hear from those who are doing it themselves and hear their opinions. But again, from what I've read, they do seem to be more beneficial during flowering. Certainly I have not read many reports of people being disappointed with them. I would try CMH bulbs in a heartbeat if they made them in 600w.
