Don't sweat it. The simple general way to handle these kinds of exits is to just walk up to the appropriate person and say, "So, I have some news for you. I'v

Don't sweat it. The simple general way to handle these kinds of exits is to just walk up to the appropriate person and say, "So, I have some news for you. I've decided to pursue an opportunity at another company." And then if they ask, you can start going into the various factors you've listed above (all of which sound perfectly legitimate). In fact there's one little nugget in your writeup which cuts to the heart of the matter, and while they may be a bit disappointed to hear you say it, it's a perfectly fair view for you to hold: I feel like I can't be the best or do the work I am good at. The basic point with this approach is you don't have to hit them over the head up front with your laundry list of negatives. By waiting for them to ask, you're making sure you have their permission first before telling them things that might hurt their feeling. (Not that you should worry so much about hurting their feelings. After all, it's just business).