I bought mine last year with the intention of running dual boot, but i haven't found the need to yet. The main reason in buying was for: the battery life (12ish hours) that hasn't been matched by any windows ultrabooks, the unmatched trackpad and form factor, and a rock solid OS(not as many conflicts running preconfigured, limited hardware sets). There really isn't much of a premium price compared to other ultrabooks. I'd recommend saving almost 300 dollars and downgrading to the 256 GB ssd, because apple does like to charge an absurd amount for certain upgrades. Unless you need to keep ALL your music and movies on there, you just don't need the space for that price. Anyone that tells you they are more expensive are wrongly comparing them to a standard laptop. Compare it to other top ultrabooks with the same specs and you'll see it falls right in line with pricing. If it's just a tool you need for the cheapest price possible, you'll obviously find better elsewhere.
Be aware: Apple will be refreshing the MBA line-up shortly and most likely adding the Broadwell/Retina line soon after within the year.