I don't really expect anyone to type these in by hand, for the few URLs that fit that need (those that are run for a specific campaign for example) we use a slightly different syntax that there is at least some hope of remembering: http://ch9.ms/glimmer for example.
As to the other points, yes URL Shortening is bad and evil, but no so bad or evil if you control your own. That removes the 'what if it goes away' issue (it is under our control, so the risk is the same as for any of our C9 URLs) and makes it slightly more clear where you are going (at least you know you are going to one of our sites).