I can't say that I agree. For certain use cases, the localStorage API is great. For example, I have built an online Text Editor (http://wrrrite.com) and I don't see any real alternatives to storing the text locally.
Nice app but I quickly got to a point where the UI became unresponsive and digging into the CPU profiler it was all in storeValue and setItem, granted some of it can also be the issue of reading the data from the DOM, but I the point stands, localStorage's synchronous API causes issues.
It all depends on the app, but we seem to be using localStorage for all our storage and bolting complex querying on to it etc and this is a huge recipe for disaster.
