This isn't quite true, as others have mentioned throughout the thread, JIRA Cloud is noticably slow to use, to the point where doing non-trivial stuff is frustrating - page loads take several seconds, and most operations require a page load. I'd expect their hosted version to offer the best performance, but apparently it doesn't. It's not unusable or anything but it's definitely a very sluggish feeling experience compared to a lot of the SaaS we are used to.