I have used the 270, 280 and 30-06 over the years.
Still own a 30-06 (LH Sako L691 with mannlicher stock) and bought my daughter her Rem 700 Titanium in 270 and as that was the rifle she preferred after testing several various rifles/cartridges.
My father was a devout 30-06 fan, his younger brother a great fan of the 270 (as they could never agree on anything! LOL)
I went with the 280 just to be a little different, and really liked what I had found in my research before purchasing my first 280 in 1988 (Browning A-Bolt Composite Stalker).
First rifle I handloaded for just over 30 years ago now., and found that it the loads I developed were performing better (accuracy and on-game performance) than the factory ammo I had been using in my father's 30-06 and uncles 270 over the years previous up to that point.
Have had 2 Rem 700 Mountain rifles since, but just could not get one to shoot MOA, even with load development, so never kept them long. Love the rifle, just couldn't get them to shoot as well as I was hoping for.
I have also used the 7MM Rem Mag quite a bit and also like this cartridge, particularly with the Federal Premium 165gr SGK ammo. Handled elk, moose, deer and mountain goat very well.
The 280 AI is intriguing, and I may try it yet, but is not on my priority list as I have other rifles that can shoot farther/flatter than my 280 (7MM STW), and I really need to get it out more!
Have to say though that the 280 holds a special place in my heart. Probably because it was the first rifle I bought myself and was the first cartridge that I handloaded for.
I now have my dream 280; a semi-custom LH Rem 700 XCR with a 24" fluted barrel that has been pillar and glass bedded into its factory stock for bad weather/rough country hunts and a LH REM LSS stock for the nicer weather/friendlier condition hunts. I can now swap stocks without shifting POI. This rifle shoots the 140 gr AccuBonds very well (1/2 MOA or better when I do my part). It also likes the 145 Barnes LRX loads that I have developed so far in just trying out the bullet when it was first introduced. Haven't it on game yet.
Am looking forward to trying the 150 gr AccuBond bullets in it, as I use the 140 AB in my 7mm-08 and the 160 AB in my 7MM STW, and would like to use a weight in between.