Actually, if you use an accounting package like QuickBooks, GST is fully supported and overall handling the GST takes almost no time at all.Well this was irking me so I called CRA and to their understanding of the business model I do need to charge GST....yay more paper work, douche bags.
If you aren't using a package like that for invoicing and you are big enough that you should be collecting the GST, I'd strongly recommend you spend the $300 for it. Well worth the investment.