Electronic – arduino – Unlabeled Headers/Pins on Arduino Uno

Last time I looked the Sparkfun Speakjet shield did have stackable headers? Anyhoo aside from that moot point- It depends on how permanent your project is.

If you want to be able to use the Arduino again with different projects or shields - it's definitely recommended you get some stackable headers because of the cheap cost and ease of use.

If the project is relatively permanent and you don't intend on using the Arduino again in another project, soldering the wires on might be better for you, it will be cheaper in the short run and will be affective for making good connections - it's just fiddly to do and not the most professional looking way of hooking stuff up.

I suspect that most shield designers either don't think of it or run out of time. When I've made shields (for personal projects), I've had intentions at the start of adding other features, but by the time everything is laid out, I just think, "OK, this will work. Maybe I'll add that other stuff on the next rev."

Adding blank holes for hacking on extra stuff is a great idea. Given that most (all?) of the shields on Sparkfun are open hardware, why don't you make an improved version? I suspect that the Sparkfun folks would be delighted to accept your improvements.