Corbyn defeating the red Tory candidate is obviously good and makes a difference by giving the public a voice of reason during the rule of an unchecked red Tory regime.

His win is significant by demonstrating that a good candidate from the labour movement with sound politics can win, even when up against the full weight of the red Tory machine.

He will have no power over government though and he is just a single guy. He is also old and can't be expected to go on for much longer. If his victory is going to be good for anything he needs to use it to build the foundations for something better, like organising an opposition party together with leftists progressive forces all over the country.