iPad will be available on 3rd April in the USA, it has been officially announced by Apple. On 12th April the next batches of orders are arriving, as the preorders are sold out.
However, for Canada market the international iPad will be available late April, as stated by Apple. Apple declares April 24th as a “black out period” for the Canada apple store employees and that means no employees are allowed to take this day off. It seems to be the launch date for iPad in Canada.