Actually my first thought was that it could be an interesting chip for us on something like the FPGAArcade with it's DSP like abilities, at least until I read that it can't be reprogrammed. I'd really like to see what could be done with it for flexible mesh vertex processing, image manipulation, MP3 / video encoding & decoding, audio effect processing, particle engines, physics simulation, etc.
I've been thinking for some time that it would be handy to add some SPI ports mapped into a convenient spot in the Amiga's address space. Then you could tack on some custom chips for CPU hungry tasks like MP3 decoding, TCP/IP stack and so on. I guess it depends on how much space is left over in the FPGA after you wedge an Amiga in there.