This course is run at the school that I work in. The course at our school has a strong popular music focus. The details from the BTEC website can be found
here.It is very different from A level music, from what I understand, and so is accepted more for popular music degrees and similar than for more classically baised music degrees. A levels are still more widely recognised, and offer the chance to study a wider range of subjects in the future. Some high profile universities and employers will always regard A levels as the qualification of choice. However, I have seen students with BTEC Nationals in music go to music colleges as well as to study music degrees at university.
Hope that helps.
Lis