My first few months as a 2P have been wonderful. I've felt more personalized customer service, and E+ is simply the best domestic coach product in the sky. ^

But UA's upgrade program has really blown me away. I'm batting 1.00 so far -- 4 for 4, using various paper and electronic instruments (no miles). It's been a pleasant surprise. Based on many of the posts here, I expected to secure upgrades only every now and then as a lowly 2P, especially considering that I fly almost only with S and T fares. So it's been a real treat!

I suspect that I would not be enjoying similar success with AA, DL, CO, or NW.