For someone with a dally driver who just wants a couple of extra mpg this mod is a no-brainer. Buy the filter (pref with the radiused inside area...bellmouth)...remove the top of the airbox...install the filter. You're done.
I've had one of the cheaper brands...probably Spectra on two cars and I use a K&N cleaner/oiler kit...and it's still in good condition.
If you run "fast and furious"...buy the expensive stuff...and have it anodized?
2003 2dr ZX3 2.0 L Zetec auto 205/50/16s
...and I am unanimous in that position.