Rad is definitely not my experience.

I've spent A LOT of time trying to get my site's appcache functionality to the point where it's barely usable. Probably more time than all of its users would have spent downloading the resources it was supposed to cache. It has more gotchas than anything else I've ever experienced.

This is incredibly accurate: http://alistapart.com/article/application-cache-is-a-doucheb...