Lots of the private schools are opting to use them as they have no coursework and are reminicent of the 'o' level. (Way before your time) They certainly won't harm you in any way with colleges etc.
I like the Edexcel Maths IGCSE, it's the one I teach for my private candidates. I think it is the best Maths syllabus around. I don't know about other subjects.