Yup, it's like your first baby and then your second one, first one was tough and needs to be looked after a lot more, the second one just came off the assembly line and fit straight into the pram.
Jokes apart, 1 gen is the first lot of commercial processors sold out in the market after the processor has been designed , prototyped, tested and finalized.
Then, after and while, recovering the costs that went into making that processor, the company is still looking to improve it's processors, so while we are using them and giving a feedback, the company is also looking into what all can be optimized, so then again comes slight changes in design, minor altercations, samples, testing and gen 2 is now out in the market.
So the basic difference between the generations is Optimization.