Sorry to resurrect an old thread, but this is what I intend to use on my build too. The guy that is driving the project runs an MX5 so it should be straight forward.
It's not intended to be a replacement for some of the higher end off the shelf ECUs, but it does fit well with the build it yourself idea.
I was looking at the BOM of materials and it came to about £40 I think (I've got the spreadsheet for it all somewhere). The designs for the PCB are opensource and we can have them printed anywhere. Might be worth doing a run of them?