Hey all-
Just wanted to give my input on this:
The bulb compatability issue has to do with how many HZ the digital/electronic ballasts run at. Line power at 120v in north america is 60hz. The ballasts take that and ramp it up to 400/600/1000w, and increase the hz (the amount of times the power comes in pulses) to 20,000 to as much as 100,000 hz. This can cause bulbs made in a certain configuration to actually physically vibrate.
This vibration is so fast that it can create a harmonic resonance - the bulbs will emit a high pitched sound. Even if they don't make noise, they're still vibrating themselves to death.
Ushio bulbs (as well as Sunpulse bulbs, what I use in my 1k lumatek) are made to prevent this from happening. Other bulbs really aren't designed for use at such a high frequency.
Between
Ushio and Sunpulse, I chose sunpulse because they're MH bulbs, and so far as i've read MH has a pretty good record. I like the idea of more blue, as I believe that's what stimulates trichromes/flavour/color.
Whatever anyone decides to do, all i'd recommend is if you're going digital, make sure your bulb is designed to handle it. El-cheap-o bulbs will "flutter", turn strange colors and blow up :P