Easy to install - instruction manual is clear and easy to follow.
If you're using the screws, put them in first to prime the screw holes! It'll take moment for each screw, but it'll make it easier (and quicker) to put them into the case afterwards.
The extension cords made it easy to combine multiple fans onto one header. Be sure to read the labels - one wire is an extender, the other is the low noise wire. (Last one is a Y extender for multiple fans. Easy to zip tie once you're done!)