Hmm. Appears to work as advertised, and with Ziru's suggestion takes me to all-new Y! mail (what used to be beta), which is how I prefer it, but a) it takes me to the US version for some odd reason (I have a yahoo.com.au address), and b) watching the status bar during loading strongly suggests that the request is rerouted a time or two, which I'm fairly sure makes it take longer than it needs to.