It's definitely not categorically malpractice to not use Word. Depends entirely on the situation. If a court demands docx and you file an rtf, or you refuse to read a client's redlines because they're in Word, sure, that could be malpractice.
The only proprietary software that I think _might_ be malpractice not to use is a legal research service with a capable citator, like Westlaw or LexisNexis. If you rely on a case that was overruled, you can't defend a malpractice suit by saying, "I didn't want to pay for the software."
I hear CourtListener (a free legal research tool) is working on a citator--hopefully it's competitive with the paid services.
[–] weitendorf 10 hours ago
It's a certainty that your clients and colleagues will be using Word to work with you and the rest of the legal system, and some files will use docx.
It would be pretty bizarre to turn down work or make things harder for people outside your firm because you refuse to use Microsoft Word.
You could use another tool that handles .docx but if it's not directly compatible with Word you're almost guaranteed to run into compatibility issues or maybe serious errors. If you don't even touch Word at all, then the first person to run into them would might be your client. Do you not just immediately decide that it's not worth saving $100/yr to eliminate that kind of risk? If not then you have to say something like
"Actually, it's more important that software be free and open source than that thing you pay me to do for you, that costs about two minutes of billable hours, and which every other lawyer uses?"
Obviously there should be lawyers trying to use open source software, but I can't believe a real person would never run into compatibility issues. Richard stallman as a lawyer explaining that he can't open files sent in formats that do not respect user freedom is such a good bit
Even if. it's not just the citation graph. No headnotes. No restatements. They're about 100 light years away from being close to usable, even if the citator was complete and comparable.