I totally agree with you guys! Personally, I'm more familiar with his chamber music. He wrote sonata's for almost every classical instrument with piano. Right now, I'm working on the flute sonata, which is nice. More impressive are the sonatas for trumpet, for viola and certainly the one for trombone!! The piano parts are rather virtuoso, but always pianistic.
Together with Martinu and Janacek, I consider Hindemith as one of the most underestimated composers of the past century. His writing can get so intensly painfull... very touching music indeed!