GST in canada is only charged to canadian residents - if an item is shipped outside Canada - GST should not be charged. If you travel to Canada to buy an item, you can still get your money back by filling out a form at the border.
For most of us who want to sell on eBay this doesn't change anything - we won't have to charge GST.
For buying, we will have to scan for the added tax. But, if you look at the bottom of each listing (near shipping info) you will notice that most power sellers may have provincial/state taxes - so this will just be another line listed there.
When I look at a listing I first check the number of feedbacks. If the number is in the thousands, you know its a business.
So, in summary, this is not earth shattering news. Keep moving, nothing to see here...