I have always considered the arranger a true instrument. In the sense that it must be learned, practiced with, and explored fully. Yes, it is different from learning a horn, or guitar or even piano, but nevertheless one must learn to play it and being familiar and using the technology is a part of it.
I can play trumpet, organ, guitar, bass and drums, to various levels, but still consider the arranger the most fun and the most challenging to play.
I fully understand the point Chas is making, and I agree, but one shouldn't need to defend using an arranger on an arranger forum, or using the optimum technology for your needs or desires!