Series composer Hashimoto Yukari 橋本由香利 must be given due credit for contributing to the excellent mood this series has generated. The writers can only go so far without music.
http://ja.wikipedia.org/wiki/%E6%A9%...A6%99%E5%88%A9
From her wikipedia entry, she's only previously composed for a live-action series back in 2003 and an obscure anime series before Toradora, though she's composed lots of anime OPs, EDs and image songs, including "Orange", which is growing on me day by day.