I worked for Viking for a while. The D1 is an Excellent machine. The fact that the designs are on floppy should not be a deterrent. Because the format of the floppy is a propitiatory format as is the file extension of the designs, you do need a program to write to the floppy (you can not just drag and drop). There are several programs out there that do that now. Of course 4D/5D will do it (both Viking and Pfaff versions) there is/was a " 3D Organizer" program which came with the machine that would do it. That program however does not run on the newer operating systems (to my best knowledge) but 5D organizer will as well which is available. There are as well as a handful of other programs. There were a couple of threads recently right here on this topic with several possible solutions.
IMHO - what ever you do - if you purchase the machine - do not in any way let a Viking dealer talk you into the USB upgrade. Because the software to "run" the USB is actually "loaded" right on the the usb stick and it must run first and the transfer of files and take much longer. The floppys are still available and work just fine. When I worked - we had many clients who had wished that they had never done the upgrade.
If it is a good price, you like it and it is within your budget - it is a great machine and should service you for a long time.