I've always liked the .280 Rem and I've owned 2 of them over the years. The first was a Remington 700 Mountain rifle which was a great gun as long as you didn't want more than 3 shots out of it, they'd start walking off the paper after that which made for a long sight in process. Incidentally that rifle was stolen and never recovered. The second a custom built benchrest gun which I still own, built on a Mauser 98 action that gun is more accurate than I could ever hope to be. I love the cartridge but if I were looking for something I could buy off the shelf ammo for it would be a 7mm-08 as it's a lot easier to find around here. Since I reload this isn't an issue for me and I would love to have another Mountain Rifle in .280 Rem.
I think the things that contributed the most to the demise of the .280 Rem (not that I think it's obsolete, not by a long shot) was a) Remington's decision to change it's name to 7mm Express and then back to .280 Rem which created a lot of confusion and b) Remington's introduction of the 7mm Rem Mag.