I did buy this tool when I was building my first kit. I didn't find it any easier or more accurate than freehanding with an Exacto.
I do have the covering film trimmer from the Harry Higley website. It works OK, but I usually can get pretty straight lines with just a sharp razor blade.
That wing bolt drill guide has me puzzled. Is it really that hard to drill and tap wing bolts that you need a special jig for it?