As one who flies on Air Canada internationally, I highly value my top tier status.

I don't pay any more than I would if I flew on other airlines but I will pay up to $400 CAD (about $300 USD) for transoceanic flights to upgrade some flights (we have two types of upgrades, some from mid-range discount fares and the others from any fare). I think the price is worth it for 10-14 hour flights.

The key benefits that I would lose are:
rewards--access to any unsold seat (not just reward seats) if plane is not oversold -- huge benefit for last minute travel
upgrades--virtually unlimited upgrades for the routes I travel as I earn enough to keep getting new ones (2 every 15K qualifying miles plus 6 to 8 at beginning of year)--huge benefit on long hauls

other not so important:
lounge access--not a big thing as I could probably buy this one way or the other for a few hundred dollars but it is a nice added benefit that I use frequently (and we still get some food and free drinks in our lounges)
elite check-in--not a big deal anymore with kiosk and online checkin but there are times when I can't do kiosk etc and elite check-in is a big benefit over long line waits
concierge service--this has meant the difference between getting on earlier flights and not when I have had tight but doable connections

Overall, I must say that for trans-oceanic travel, I would really not like travelling so much without status. It just makes most things go so much more smoothly.

For North American travel, I might not miss it as much (but haven't been put to the test too much on this). I can stand several hours in coach provided I get Economy Plus (e.g. UA). With recent changes in my program related to North America, I would be inclined to look for another program/airline to fly on and not necessarily go for status without a careful look at the benefits.