Reasons I wouldn't get it: It does not appear to have parabolic reflectors, though it does at least have individual reflectors. No waterproof endcaps. They don't mention what ballast it uses and not all ballasts are created equal. Also, it almost certainly comes with inferior bulbs that will not have the color, nor intensity of high quality bulbs.
If you want something better than PCs (might even be a SLIGHT upgrade to your VHOs) it could be an option, otherwise I would pass. If cost is an issue you could consider doing it in stages with Sunlight Supply's Ready-fit kits, or simply buying 2-4 bulb retrofits at a time. Check
www.reefgeek.com for some of the best prices and a great selection. Personally, I'd probably keep 2 of the VHOs for actinic and then add 4 T5s.
Just my thoughts, hope it helps.
edit after reading Luke33's post that he was typing at about the same time as me: By the time you replace 8 inferior bulbs with 8 good ones at $20+ a piece you could have gone to Reefgeek and gotten a 6 bulb SLR retro with top shelf bulbs that would blow this cheapy away.