Though this should be in the General Tech section, but I can understand the lack of traffic over there.

The idea of relocating the filter is a good one. Getting under the intake manifold can be a bit of a PITA depending on your m/y. I know the NB2's intake manifold makes it a jolly good time. So the main benefit is ease of changing the filter. As long as you use good, reputable parts, or a kit from a reputable company, there should not be any negative side-effects. Some claim that there is a pressure drop, but no one has ever backed that claim up or have been able to prove any ill-effects of a relocation kit. I have heard some reports that the firewall mounted kits introduce some noise into the cabin, but after having two NBs with these types of relocation kits, I have never heard a bit of noise from the relocation onto the firewall. I currently have the FM relocation kit and it has performed flawlessly. An added bonus to a good relocation kit is the ability to add an external oil cooler later down the line if you decide you need to. I do not have one, but have definitely thought about it since I am turbo'd.

Honorable mention- I added a FM relocation kit to my GF's Mazdaspeed Miata as well, never had an issue with it. So that is two cars in my garage with relocation kits.