I personally haven't seen or used these. But, just by looking at the fixture/specs I would be kinda leery as they use magnetic ballast, which are considered "old technology." They are large, external to the fixture, heat up a decent amount, and tend not to have the lifespan as newer electronic ballasts. Also I can't tell but they dont mention the use of fans, which is a potential for a big issue as far as heat on the bulbs and tank go. Any specific reason you were looking at this fixture and not one w/ T5 or PC actinics? Most people also like the actinics as a chance to run their lighting a little bit longer and get more light into the tank.
Again I haven't ever handled one of these so I could be completely off base here just my thoughts/opinions based off of what I could find quickly on the web. If somebody has worked with these before and I am wrong feel free to say so, I just thought I would throw in my 2cents.
yeah after i read a little more it kind of made me forget about it so i think im just going with 2 metal hailde pendants instead if i can find them for a good price