I know that most of you will not leave your lenses and cameras in your main checked-in luggage. I wouldn't. I carry all my gear in a Lowepro Slingshot AW300, which isn't exactly SMALL. When I travel, I usually have to bring my laptop (for work) and maybe another bag for clothes, toiletries etc. I can squeeze all that in to the laptop bag.
Has any airlines ever given you any problems for carrying so much 'carry on' luggage? If they were, what do you do?? You can't give up the laptop OR the lenses / camera..... Technically, only 1 piece is allowed weighing no MORE than 7kg.