sidemount --
the ACSO/Air Nav occupation is going through changes as the CF tries to figure out which airframes and air communities require a nav. You probably know that navs are employed in 4 different communities: AirMobility/SAR, Long Range Patrol, Marine Helo, and Electronic Warfare. The day-to-day job is very different depending on the community in which you're employed. There's also the (possible) UAV community. The higher ups originally though that this would be in full swing by now but it has been delayed. There are many ACSOs in the training system now, clogging it up. I believe the original thinking was to push more through so that they could be increasingly employed in UAVs and EW. But since that is not currently the case they have been pushed into other communities which are already at or near capacity (plain english = long training delays).
A nav in SAR would be working shift work, on-call etc. in order to provide search and rescue readiness at a sar squadron. The job involves a lot of system manipulation, understanding of flight planning, weather, search patterns, effectiveness, and radio comms. There is some question as to whether navs will continue to be a part of future fixed wing sar, but nothing concrete.
Long Range patrol would be Aurora aircraft on either coast. Longer missions and the job specifics would be either (1) comms manager and maintaining the legal log or (2) tactical nav...effectively coming up with the plan and putting it into action, along with the rest of the crew.
MH is the Sea King/Cyclone and the nav is the tactical commander. He runs the whole mission from inside the aircraft. Probably live on ship for a few months out of the year on deployment ops. Recommend you try to get a ship tour at some point since it is not for everyone.
EW would be the alpha jet out of Ottawa. In this role, the nav becomes an electronic warfare expert. The sqn basically plays a training role with the army, air force, and navy, and can emulate a wide variety of EW threats. The nav is the expert button-pusher extraordinaire.
Since everyone attends the basic nav course in Winnipeg, it doesn't prepare you for one specific community but more of a blend of all of them. Whatever community you're working with, job emphasis is big picture planning. I like to think that the pilots focus on the safety of aircraft and crew, and the nav focuses on the details of the larger mission. Weather, electronics, airspace & airmanship, comms, legal logging and whatever the mission is are your paramount concerns day to day.
It's hard to summarize. Hope this helped.