Most popular ones I've seen here are Injen cold air and AEM ram air. I guess a bunch have Ractive too.
Performance-wise they both seem to provide the same gain, which is not a ridiculous amount.
Looks it's really up to you, but many agree that the Injen just looks way better.
Price is a major thing for most since the Injen goes for $195 and the AEM goes for $140. Not a big difference, but it's there.
I think everyone's been pretty happy with whatever choice they made, except for those very few who happened to drive through a deep puddle while using a CAI. There is a bypass valve you could get to solve that problem but most people don't really drive through puddles that deep and it seems to cause no problem during downpours. Plus, some claim the valve takes away some of the performance gains.
Other than that it's just personal preference. I got my Injen because I love the way it looks and know I won't be fording streams. Some are more practical and chose to build their own or get a "generic" one from Ebay or something.
There are plenty of other choices for intakes, like the K&N Typhoon CAI (for a cool $400!!) which looks like the Injen, but in the end it's really a personal preference.
And I have to say that the ones that get CAIs are the ones that are more confident that they won't drive into a puddle and cause havok.