I have one 81DL loop of 3/8 square filed and a couple of files. I played with it until I could file it reasonably well, and even made a new vice so I could file it properly. It was interesting and marginally faster, and I'm glad I tried it, but it still takes me more time to sharpen it and the files are much more expensive. I can buy good Stihl round files at the local hardware store for around $4 for a 3 pack, and no shipping cost. Also, if I damage a cutter I cannot fix it up on my cheap grinder, but have to do the repair by hand.
My preference is really for semi chisel, and I don't really need a 24" bar very often. When I do I go for the 25" bar and a loop of 75DPX before I go for the square grind. At this point I mostly save the square grind for falling when I need something larger.