I just started doing some game development myself about 5 months ago. I have been using Unity for most of the time and I think it has been the easiest engine to work with for new game developers. That said, I am working on a 2D game. I am not using any plugins from the Unity App Store. I program for a living and from the sounds of it, you know more than enough programming to use Unity. Also, the thing that really got me interested in Unity is the ease in which you can be platform-independent with your development. Yes, you will need to pay for those, but IMHO you shouldn't worry about multi-platform until you can make up the cost with previously released games. Baby steps.
There is the downside that I don't think the documentation on the API is 100% accurate and complete, but with the ever-increasing community that comes with Unity, you can't really lose.
Like other have said, in the end it's a matter of taste. I am OCDish in the way that I always want to use the *best* technology, but many times, there is no single best software for doing everything. Just try out a bunch of engines and see what you like.
Developer
