Having leased a few times (Honda and Subaru), I had no problems turning them in early, over mileage and with worn tires, but the key there was, I had something in mind on their lot I wanted to buy and turn the lease in for. I just made it clear that if we can strike a deal on that vehicle and you take my lease in free and clear, it's a done deal. Otherwise I'll go elsewhere, which you can absolutely do at any dealer with a lease. They will deal with your lease company if they want to make a deal with you.
Make sure you understand what the residual value of the vehicle is going to be at the end of the lease and any associated fees in buying it out. You want those terms to be reasonable in the event you want or need to buy it at the end. Sure you are going to pay a bit more than if you financed it in the first place, but it just spreads your payments out for a longer period of time. Again, not the wisest financial move, but what is when it comes to vehicle ownership.