I get where the OP is coming from. I was never underwhelmed with my Series 3, but initially I was unsure if my Series 3 was really worth the extra price. Especially considering I had horrible battery life the first couple days. I got the Space Black SS Series 3 and had the Space Grey aluminum Series 1. I don't find the SS to be as comfortable as my aluminum either. The extra weight of the steel and the ceramic back that juts out farther than the composite one on the aluminum just didn't sit right on my wrist.
After a couple weeks though I decided the upgrade was definitely worth it for me. (YMMV) The battery life is crazy good in comparison. I went almost 3 full days without charging recently!!! I couldn't imagine my Series 1 lasting that long. I've gotten used to the weight (but not the thicker back). And although I haven't used it yet I really appreciate the extra water resistance. I'm a compulsive hand washer, especially this time of year, and my hands are often in water at work. With my Series 1 I was always worried about getting it wet, but not anymore. The Space Black is something I've wanted since Series 0, but I've never been able to wait until I could afford it. My Series 0 and 1 were both the grey aluminum.
TL;DR The Space Black, extra water resistance, and much better battery life really make me appreciate the Series 3.