One additional post script: the entire philosophy behind the parabolic design is to focus more light on the subject even though you're bouncing it off of a reflector. To experience that advantage, the silver PLM is the only one that makes sense. Now, when I saw what it could do in my particular shooting situation as a single light, that was a secondary advantage I didn't expect. The third is that like regular umbrellas, the PLM is very portable and because I do a lot of on-location formals at shows, it's much easier to travel with than other Light Modifiers such as softboxes. And, lastly, they're cheap!

So, let's review:
1. they kick out more light than comparable umbrellas
2. they provide more spread and therefore more coverage than standard umbrellas.
3. they are light and ultra portable
4. they are a great value in terms of lighting performance/dollar.

Even if I don't use it everywhere or in every situation, just having it in my bag of lighting tricks is a major advantage.

Jim