I myself know little about the TERF's, mainly because I can't see wasting any of my time on people like that. But my impression is that they're a (very) minor irritant and nothing more, especially compared to other threats such as religious fundamentalists. I can't imagine that anyone outside academic circles would pay any attention to them. E.g., in the little town I live in people are very friendly to me, very accepting. You're talking about plain old people--post office clerks, supermarket cashiers, that sort--who don't have anything to do with any sort of feminism, let alone the radical crowd. If the TERF's came into this town trying to stir up opposition against me, people would think they're the crazies, not me.
I came across one measure of their support not long ago. Now you probably know of organizations like All-Out that often start up petitions in support of various LGBT causes. They've got their act together, and whatever the petition, they can get tens of thousands of signatures in a matter of days.
Yet there was once an incident in which Catherine Brennan got tossed out of an LGBT pub. Her supporters tried to get a petition of protest going. When I saw the petition, it had been posted on line for a year and yet had only about 50 signatures. Fifty in a year, compared to the tens of thousands our side can get in a few days. That's the measure of support the most famous of TERF's has worldwide.