I never heard about it until I started with my new company and old workmates didn't really know of it. The ones who did have qualifications generally had some kind of IT based qualifications. I got most of my knowledge on the job, but the course and certificate cemented what i had learnt which i found useful.
PS today is my two year anniversary of moving to canberra and starting in testing.
Although this is a late reply, I'll put in an employer point of view:
We've known about ISEB for more than 5 years I think, but no-one does it unless funded by an employer.
Most senior people in testing that I have met share my point of view to some greater or lesser extent: Certification with ISEB or other similar certs is next to worthless when considering someone for a role. In fact, it makes me suspicious when I am hiring. (Why did you certify? Didnt you think you were good enough on your own merits?)
The only reason to consider it is if you are applying through recruiter agencies who don't understand testing. They are starting to ask about it (and sometimes demand it)lately because they have the idea that if you are certified then they dont have to worry about how you suit the role, they can just throw you in there and you should get it.
The reality is that I have seen too many inexperienced people trying to punch above their weight in jobs they got through theoretical documents. (this is true outside of testing also)
My considered opinion is that it is much better to go for a slightly more junior position at a company with a good public reputation for process, etc. A couple of years of that is worth WAYYY more on a CV than a rubber stamp from ISEB or anyone else.
"Not every solution was derived to address an obvious problem" - Me (quite recently indeed)