I have one - got it around the July 4th sale I think?
Installation was easy enough - had a hard time getting one of the stock hose clamps off - was really tight and I didn't want to break it so it took some effort.
(my last aftermarket air intake was back in 2002 on a dodge stratus coupe from AEM so... so I'm sure things have changed since then, lol... excuse my trying to explain stuff)
As for the intake -
I like the sound. Kinda almost a snorkel sound maybe? I can't quite put my finger on it. Starting the car when it's cold out is super loud / almost annoying but after a minute or so the rpms level off and it gets quieter.
I ran it for a bit without Steeda's tune while I was waiting for it to come. As I said, it was around the 4th of july sale so I'm assuming the tuner was busy. I get gas at the same place every time so I had it done for their air intake and 91 octane. You can feel the power difference over stock for sure, but I haven't gotten a dyno done. It's seriously a different car with the tune.
Low rpm is still a bit soft but that's no fault of Steeda or the tuner I don't think. I get lots of power around 3500+ RPM. As much as I probably shouldn't discuss it here, random street encounters have proven it a win - from WRX's to most Dodges including their Hemi's - few have beat me. Corvettes never want to play and we don't have much fancier than that here. And I have a convertible so she's a bit heavier, lol...
I had the tuner at the top of the windshield driver side until a week or 2 ago and moved it to the passenger side on a mount. Much better there. I know it's not needed after the tune, but the live wire is so expensive - a: may as well use it and b: I like to see the gauges - it's fancy IMO.
It's my first and probably only CAI on the Mustang so I can't compare it to an AirRaid or anything else - but I'm happy.
I have the Steeda CAI with tune for the automatic transmission. My Dynojet runs ended up with 297.31 rwhp and 343.60 torque with CAI and tune. With the CAI only it was 278.69 rwhp and 309.23 torque. In the Sport mode, the shifting is much better. I can get through corners much faster because down shifts leave me at a lower rpm, where I have more torque. The stock tune down shifts to a high rpm where I do not have the torque to accelerate. And now that I have added a Magnaflow Street Cat-back, I have a few more ponies and a much better sound. Since having it installed, I mostly drive with the radio off so I can listen to the exhaust.
I am finally getting my health back to the point where I can take my Mustang out and have some fun. If I get a nice weekend where I have no plans, I am going up to the Tail of the Dragon to have some fun and see what she can do.