When I was a student, the company I was working for during the holidays was very keen on IEE membership, and signed up all the apprentices for it.
I left them on graduation, and never actually went as far as getting full membership and a CEng, though - and it's not affected my professional career in the slightest. I've only ever even met one or two members that I'm aware of, and nobody important has ever suggested to me that I should join.
Personally I'd be very wary of companies who consider the extra letters after your name as being more important, or even anywhere near as important, as your skills, knowledge and interest in electronics.