Sooooo, I did this a few weeks ago, not PERFECT but we'll see how the deposit check looks.....if there's one at all (hooooppefully not ADDED charges) I figure there's always plausible deniability.
With a strong light (it's in the hallway) you can definitely see some edges. This is due to me kind of ghettoing the drywall piece to be flush by taping some layers of thinner cardboard behind the piece, up against the left and right lips of the studs (can't see the right stud in the picture). Looks like I overdid it in the upper left, and the opposite in a few other areas.
Also, I ended up taking the special tape off. It refused to stay on, even with the compound behind and on top, and I figured I could just apply more and sand it smooth, or even use spackle.
All in all, I think "OK" job for a first time, but if this was my home, I'd redo it. And it would probably go 5 times faster, haha.
Actually, that texture aerosol spray ended up making it blend better than I thought. Was surprised at the effectiveness of that stuff.