Hey, I'm one of them! My series 0 has treated me well, but it's time to move on. I just figured I'd get 12 hours to get an order in. Luckily, I did at Best Buy.
This all comes right as the temperature is going to start dropping, and I'll start swimming more at the gym again. (Spend most of my time running outside when it's nice.) It'll be rad to keep the watch on when I'm doing laps.
My girlfriend uses the Series 3 for swimming (and triathlons in general) - swimming laps can be hit or miss, especially when there's no proper GPS coverage.
Myself, I just want something that i don't have to put on its charger for 20 minutes after i get home from work at 5pm, just so it doesn't die on me during my run :(
Like, i wouldn't even have to bother going on some winter runs with my Series 0 - these sub-zero degrees kill the battery no matter what charge.
I was so happy the Series 4 is such a meaningful upgrade.