I am actually going to be putting one in my fuge. I have a large fuge, I just need to find the right light... Only really good for certain things, since the flow is slow in my case.
I think you could effectively grow out in a section of the sump. However, you would need more flow. Like jpelzer stated the flow going one way may be an issue. If I can make a suggestion, decide how much room you want to dedicate to grow out and seperate it from the macro area. One thing you don't want to be doing is picking macro off your corals. Plus this will allow you to place a powerhead in that area to give more flow to the corals.
On to lighting, the best light for your corals is not exactly your best light for macro. This is yet another reason to split the section.