I liked being able to look at the seat map a day or two out to get a feel for my upgrade chances. Was it accurate? Of course not. A single flight cancellation could have wiped out all of the open seats. But most of the time, it was a good barometer of the odds.

As another poster mentioned above, I also leave C+ off my upgrade choices until I see the seat map. If a middle seat is all that's available, I don't want the "upgrade" to a less desirable seat. Jumping through extra hoops to see the C+ map by going most of the way through a dummy reservation is a hassle.

Is Delta getting a benefit here? I'm struggling to see what it would be. I'm not unreasonable. If there's a good reason for this, then I'll just jump through the extra hoops to see the seat map and not worry about it. However, since I'm not seeing how this change is of any material benefit to Delta, I'm annoyed, and will be annoyed every time I have to tinker with a faux reservation to see the seat map.