I went to Canada for 3 weeks in September, total of 5 flights. Didn't trust the baggage handlers with my lenses in my main bag, so took on a Jessops hard case.Was slightly out of the 'allowed' carry on sizes but no one took any notice. Never even got stopped at security despite the big metal box I was carrying!
There are a few airlines saying that you are allowed 1 piece of carry on plus another (they give examples of a laptop case, handbag and camera bag) but they never seem to specify how big the camera bag can be.....
It's safer for your equipment to go as carry on, unless you have a peli case. Just don't look like you're struggling with the weight and you're golden! If you do purchase a hard case to carry on, get one with wheels, it starts to weigh a lot after carrying it for a few hours!