Well, if you're a runner, then you may want to wait for Gen2 because rumor has that it will have integrated GPS. Otherwise, to path your run with Gen1, you need to bring your iPhone with you. I run on treadmill...so, Gen1 works great!
This would be a pain, but so be it.
I have the Sport band (midnight blue) as my daily band...works great daily and during exercise. Very durable...looks like new.
I can't have any band that isn't metal. My leather/rubber bands always start to stink after a few weeks with me, LOL.
But if you wait for Gen2, then expect to wait at least another year after intro for any discounts especially if Gen2 sales explodes even more. If you don't mind taking your iPhone with you on runs, then get Gen1.
My 101% guess for Gen2: slightly slimmer if at all (but still use same bands as Gen1; Apple may keep size same but put in bigger battery), faster chip (even tho Gen1 hardware is excellent as is) and slightly longer battery life due to better processor efficiency & slightly bigger battery, better water resistance for swimmers (even tho Gen1 is water resistant unofficially), and GPS +/- 3G connectivity.
PERSONALLY, I would wait for Gen3. Why? Gen2 is like the "S" series on iPhones. Very similar hardware. Gen3 will be big changes...like new micro-LED display rumored...and matched that to further refinement in processor (14nm?) and you can have DAYS of battery life. In addition, by that time, it may come with more sensors, like sweat analysis sensor (checking blood sugars etc.).
That would be incredible and worth every pennies especially for those have have diabetes, WOW.
So, I will DEFINITELY skip Gen2.