I believe looking at cartridge drawings that the 280 rem has a slighley different shoulder than the 270 or 3006, otherwise it is just a 3006 necked down to .284. THere is a great selection of bullets for it around. Very high BC in the bullet selection.
Due to the different shoulder, the .280 has slightly more case capacity than the .270 or .30-06. This equals slightly higher velocities. I think the .280 is the best of both worlds when comparing the .270 or the .30-06. It has more energy than the .270, and shoots flatter than the .30-06. With the .280, you can load up to a 175gr bullet. Some say, well with the .30-06 you can load 200gr and more. But I say, what will the 200 grain due that the 180 doesn't?
I am partial to the .280 because I own one, but it is a very versatile round. I say as versatile as the .30-06. You can load the .30-06 heavier, but why? I've read reports that once you get over 180 gr bullets, the velocities start to drop off enough that you get unreliable expansion.
The thing that the 06 has going for it, is factory ammo. You can pretty much by it anywhere. Not so much with the .280. I think the .280 really shines with hand loaded ammo.