Yamaha DTXpress/DTXplorer/DTXtreme

Has anyone here used the special serial "to host" cables that 
apparently are available to connect the DTXpress to a computer?  How 
were the results?

My rig did not come with one, but the manual shows three examples.  
Surely they must make a USB version by now?

I have looked for this cable and have not found one.  Anyone know 
where to find one?

Is it worth it?

Alex