I've been experimenting using old files to make lathe tools and currently am using one for almost all my external turning. I find it easy to keep sharp, although it does need touching up rather frequently, certainly easier than HSS and carbide. I also find that I can get what appears to be a better surface compared to HSS & carbide, although I am unable to make proper measurements. The downside is the need to keep speeds down, but for me that is of no consequence as it gives me plenty thinking time.
The initial shaping can be tedious due in part the need to keep the work cool, but it is reasonably easy, certainly easier than shaping HSS.
Best of all, the source material is free and given a reasonably sized file, say a coarse 12inch, then enough material can be sourced for say 6 tools.
Of course, I'm speaking purely as an amateur who is in it for self educational purposes, and I fully realise that this won't do for a lot of people.
Have fun, and have a go,
Peter G. Shaw