Agreed, although SpiNNaker really isn't much specialized for spiking NNs - it's really just a large ARM-base cluster specialized for fast message passing. The messages could be inter-neuron communications, or anything else, and it has been used for other purposes.

I really don't understand the thinking behind these hardware-based neuromorphic projects... as you say it would make more sense to prove ideas out in software first, especially for experimenting with more biologically accurate models of neurons.

It seems the time to commit to hardware would be if neuromorhic/spiking/asynchronous designs show worthwhile functional benefits, and need custom silicon for efficient implementation.