Since you haven't mudded over the screws, why not take down that corner sheet of the ceiling, shim as necessary and reinstall? If you have two people it's not that big a deal... unless it's glued to the joists. :)

Jon1270- We can't really do that because the corner is off on both sides: Too high on the right side, too low on the left side. We would have to float the difference all the way around the room to make it look level above all the doorways/windows. In the first pic, you can see how it droops down in the corner, then in the second pic you can see how it drifts up in the corner. So, both sides are off for different reasons, so it isn't as simple as just brining the whole corner up/down. We'd have to take ALL the drywall down and shim a number of joists. (And BTW, yes, it is glued AND screwed)

Any other thoughts?

Looking at the 3rd picture-
Looks like part of the problem is that the one wall sheet by the window is not cut/hung straight (look at the gap at top and bottom left side of window).
Another part of the problem may be the window casing may be off a bit.
Combined, this could lead to the discrepancy you see at the top.
Try removing that piece and recut if neccesary and rehang-
I'll bet you see a difference!

Rather than relying on the relationship between the sheets on the ceiling and those on the walls as a visual indicator of what's going on, I'd put a straightedge or spirit level against the ceiling in several places around there to see which way it's really sloped and whether/how much that corner sheet of the ceiling might be curved to bridge crooked joists or an out-of-place nailer.

One thing that strikes me as odd, in the first and second photos, is the way the drywall on the ceiling drops across that second joist, presumably ~32" from the front wall. The horizontal factory edge of the sheet that's on the wall over the arch is obviously straight and the joist sits on top of that wall just like all the other joists, so I'm wondering whether the sheet on the ceiling might not have been pulled up tight against that second joist.

Once you can wrap your head around why it's doing what it's doing, your options might be clearer.

Mud it in and see how it looks. We've had old houses with uneven wall/ceiling lines, wallpapered them with pattern paper, and still had a hard time finding the line without counting spaces on the wallpaper.

Looks like floating it out with many coats letting dry inbetween is an only alternative. I personally wouldn't like the idea of that much mud up there for reliability reasons, but if you have the time to build it out slow and not applying too much at once, letting each coat thoroughly dry, could be okay.

Thanks for the ideas so far.

We're thinking of putting in tin ceiling tiles over furring strips (shimmed as necessary to level things out) and avoiding the drywall mess. What a disaster.

Any opinions on this (cop-out) technique?

Consider adding a shallow soffit around the perimeter of the room. Something along the lines of 4" deep (3-1/2" 2x4 plus 1/2" drywall) by 18" or so wide.

On the upper wall/ceiling corner, make it level around the room. In some places your 2x4 will be butted to the ceiling, in the wacky corner it may be an inch off the ceiling.

Toward the center of the ceiling, butt it tight to the ceiling.

You will, in effect, be creating a tray ceiling with a 4" reveal at the tray.

I did a quick google for "tray ceiling" to get you a photo, here's the idea:

The wider you make the soffit, the more is will disguise variances in height. Meaning, a 24" soffit will hide a 1" error better than a 6" soffit.

Mongo

We have had this problem in two rooms in this house and handled it in the kitchen by dropping the ceiling down and adding tiles . Basically we just covered the problem in that room . The bathroom we just finished over the off corner and it still bothers me but monney and patience was a issue at that point.I love old houses by boy the walls and floors can give you fits when remodling.

madeyana - yes, we are considering going that route, too. Putting up furring strips and hanging a tin ceiling tile. That would be "period" for our home, too, so it would be a bonus.

Personally, I would take the ceiling drywall down at the edge where it is not level. Then shim and get it level. I know this would be a mess, but it will probably be less work than trying to get this to look right - that is quite a dip, and yes you will notice it. I know because I had to merge 1/2" (or 3/8") with 5/8" on my ceiling and the the dip was noticeable. And your change is much more than that. If you have to install the new ceiling drywall without the benefit of being tucked under the wall drywall, simply use extra screws/glue for support.

Can't you cut out the drywall just on that side? Cut along the edge of the nearest stud that is level, install a 2x2 nailer on this stud, shim your high stud, and fasten the patch piece to the nailer and shimmed stud. (See the page below for an example)

Here is a link that might be useful: Patching Drywall

Drywall guy - I don't think we can repair this without having to somehow float the difference all the way around the room. Because, the corner is "off" in opposing directions. If you look at pic 2, you can see how the corner drifts upwards. Then, look at pic 3 and you can see how that side of the corner droops down. So, if we fixed the left side of the corner (pic 2) then the drooping in pic 3 would get even worse. And vice versa. Thats why we're considering just furring and doing a tile ceiling at this point.

Or wood. Here's a link:

Here is a link that might be useful: wooden drops