Maybe the term has outlived its usefulness. The use here on FR got my attention because I was brought up in an organization which called itself the "Protestant Episcopal Church in the United States of America" and did so until after I was ordained, I think.
And, as I've said on FR before, it was at an acolytes festival at "Smoky Mary's" in NYC that I first saw candle racks and people praying to, ah, idols.
I've found that some Protestants on FR don't take kindly to that's being called "protestant", but that's what the piskies thought they were back then.
The Lutheran Church doesn't offically consider itself "Protestant". We're Reform. If someone calls me a protestant, I don't figure it's any big deal.
I think most Baptists are bothered when someone calls 'em "Protestant", specially those who claim their roots go back to John the Baptist.
That's because the Anglican Communion has its roots in the Reformation (I say this practically, but I know there are many Anglicans who would disagree). Anyway, when you call denominations that weren't born from the Reformation "Protestant", it probably strikes them as odd because they don't see themselves as protesters.