My native language is Swedish. I've studied English since I was 8 (and I'm 42 now), German for 3 years in school and lived there for 4, two years of Italian and two years of Chinese. It seems the more languages I learn, the more interesting and worthwhile it gets to compare similarities/differences and the easier it is to learn new ones.
Learning a completely different language, such as Chinese coming from English, has similar benefits to learning Lisp coming from Java. It stretches the brain in exotic ways.