I just got the SE. I've been eyeing a new watch since last November when the series 3 went on sale for $129 for Black Friday. That $279 pricepoint sounded really fair. My initial reaction was negative towards it (I was hoping for $199 for the S4 or S5), but really... the $279 seems really fair considering the series 5 was JUST on sale for $299 at a lot of places. I'm happy.
I've had the series 0 since almost launch day, and it's held up remarkably well, even without the latest updates!
The SE made the decision super easy since I felt I missed out (a little) on the sales from earlier this year on the series 5, and I want the 40mm design (of the S4/5/6) not the old 38mm of the S0/1/2/3)
I only like the watch for the OS benefits (many,many of them), and the fitness tracking... so I'm not interested in EKG or the blood oxygen tracking (not for $399 anyways). And the series 0 is slow sometimes opening the fitness app, so I'm concerned with the longterm life of the s3 (especially since I keep watches for... 4/5 years).
The compass is really nice for going on hikes, exploring trails, etc. so I'm looking forward to that.
And getting the dark blue band can take the place of not getting the new blue color on the s6, haha.
Edit P.s.: also, it does make me feel good to know that Apple didn't dump on people who just bought an S5 by significantly lowering the price. In other words, I'm glad that Apple didn't create buyers remorse for the people that bought an S5, by charging a much lower price on the SE.