I like these goggles, they're comfortable and haven't fogged up yet. I'm giving them an 8 simply because although the goggles themselves are almost perfect, the fan is practically a detracting factor for any average consumer in purchasing these. Of course, if your point of view is that of necessitating the fan, then you might as well assume this to be a rating of 10 overall.
The lens is clear, fog-free and dark enough to withstand some of the brightest sun while still light enough for the darker days.
The design is pretty standard, except for the fact that there is a FAN on the top. A FAN! At some point one has to shake their head in wonder at what will be next. Although the fan is perhaps a little overkill, it does serve a good purpose for those times when it's needed. It really depends on your usage habits and personality to define whether this is needed or overkill.
The goggles themselves are worth the cost, regardless of the fan embedded in the top. They work well with the Vantage series of helmets and are really comfortable to wear. I'd say the current cost is well worth the goggles themselves, and the fan is simply icing.
The Prophecy fit very comfortably and meld very well with the Vantage helmet, except for a minor gap on the forehead.
You get what you pay for. The goggles are well built and designed to last, baring any major human-driven intervention.