Hello, my requirements were very similar to yours. I've been using a Sandisk Sansa Fuze since christmas and it's pretty amazing. It does video but it's easily ignored if you want :)
8GB with a microSD slot in case you want to upgrade it with a larger card in future (it transparently merges with the onboard memory).
Battery life is amazing, I can go for weeks on light usage between charges (they state 24hrs I believe, but ymmv).
I listen through a pair of £15 Sennheiser CX300 and the sound is great, but then I'm no audiophile.
No fancy software required, you can drag and drop as a standard USB device in Windows.
It does a few other things, but you don't mention a preference so neither shall I.