I like the way of the tinyURL API better - you simply get the new URL in the body of the response. Otherwise, I am not sure it is easier to parse the XML response from unshort.me than to simply resolve the redirections directly.
There are some possible uses for such a service, I think. For example if you want to get this functionality via JavaScript (eg JSONP), or perhaps you just don't want to bother with HTTP.
(unshort.me, I hope you don't mind me plugging it here - if you do, let me know (email's in the profile) and I'll delete this comment. Looks like we're about to have as many unshortening sites as shortening ones, at this rate :)
