Ask HN: Client side storage JavaScript libraries?

Wondering if anyone has experience using client side storage javascript libraries? I am considering localStorage but not if it supports older browsers.

I am currently using cookies but it's problematic in that it's hard to do CRUD for a given key value pair. I would like something that supports key, value, JSON objects preferrable, and lets me upload these data later using ajax.

I would also like to cover as many browser as possible.