I'd say Virtex is mostly always in line with mt-gox price
when mtgox has a big move, it sometimes takes Virtex a few hours to correct itself
1000CAD -> to exchange = 994CAD
BUY 987.54CAD -> BTC = 83.12BTC after fees
SELL on mtgox 83.12BTC -> 1034.12USD after fees
1034.12USD converted to CAD through bank is 995.24 CAD
This doesn't include any fees for transferring money from exchange to your bank.
*This is just from a quick glance at both exchanges, not 100% accurate.
Arbitrage is almost never worth it.
best thing to do is buy stuff with them... since everyone use mtgox's higher rate to value the coins.