Best school/office work laptop?

I'm looking for a good basic laptop (mostly school and office work, also multimedia).
Needs to be:
15.6" screen or similar
8 GB RAM
i5 processor
Convenient to carry around in a back pack
Available for online order in the US.
I'd prefer it to also have really good battery life and a wide screen (16:10). Preinstalled OS doesn't matter (will install Ubuntu anyway).
I realise these specs are a bit above basic but I will also need it to smoothly run high def video, multi-tabbed browsing, basic image editing etc. And to still be good in a few years. I'm trying to find a laptop for $500 or less, but could be persuaded to spend up to $600 on a good product.
Please answer from personal experience if possible, and thank you (:

Read more: Best school/office work laptop?