1. Other than the ability to easily upgrade memory, am I losing anything by going with 4x4GB instead of 2x8GB?
There is a slight, unnoticeable performance boost in using the 4 sticks in both channels vs 2 sticks. Also, in general, 4GB sticks can have tighter timings than 8GB sticks at the same speed. 8GB modules, especially at higher speeds, will require looser timings and higher voltages than 4GB modules.
The trade off is that occupying all four DIMM slots makes overclocking your memory more difficult, and in the case of Haswell, overclocking is a more unique experience with its internal memory controller. To spare you the technical detail, I'll just say that the higher you overclock your haswell CPU, the less room you'll have to overclock your memory. However, this really only applies to speeds exceeding 2133.
2. If I'm not overclocking on day one, am I doing myself a disservice (in other words, will my 1440p gaming experience be hindered)?
Your system will run great at 1440p right out of the box, stock clocks. You have some time to allow yourself to learn about it thoroughly. I urge you to eventually read up on it and try it out for yourself, as you will get some significant increases in performance when one of those bad ports comes along and taxes your hardware more than it should. But for now, don't stress out about it. You're going to have enough to deal with when you start the build.