A test version was uploaded by accident earlier today, so if you've already downloaded it, check that you have the version with Serialiser v2-50 and pcb DTS1010. The correct version is on the web site now.
If you don't have your own PIC programmer, I would wait a few weeks to see if any bugs appear. With so many SD cards out there, there could be some variation in operation. If you don't have an SD card, Colin, G4KLB and myself have used the Verbatim 2GB cards successfully. These are available on eBay. Colin has obtained a number of different cards to test.
In theory, manufacturing a device containing an SD card requires a licence from the SD Card Association and software using the FAT file system requires a licence from Microsoft. I don't expect that by making one for yourself the SD Card Association will want $2000 from you to join, or that Microsoft will want $0.25 from you, but I am not a lawyer, so proceed at your own risk.
Please post any feedback here, particularly about problems.
Thanks to all who helped with the testing and to G8AJN and G4KLB for the web page.