What other thing can I do with an FPGA?
That's the cool thing about fpga's you can reprogram it to do anything, ASICs on the other hand can only do what they were originally made for.
That's a moot point

There's no way for the common guy who bought this FPGA to mine Vanillacoin, to find other uses for it.
But it compares in the sense that when you're done mining with your GPU farm are you going to play Crysis at 8k with 20 R290's?
No, it's just not going to happen, rather you sell it to someone else who does have a use for it