As far as I know, we're not talking about a new line which smashes down the A6 here. It's merely the extension from East Dids into Stockport.
Opens up Didsbury, Chorlton and the trafford area to Stopfordians. Which I would say is quite useful as all our connections seem to be purely straight into Manchester ( for example it will be a good link to the cricket ground at old trafford).
You can still jump on a nice quick train into Manchester if you wish.