I can't speak for the H2 in this matter but on the (Avalanche) 5.7L Chevy engine with both the Corsa and K&N FIPK installed I can ...
I know GM at the time would void the warranty due to the oil in the filter or if you over lubed it after cleaning it. I actually ended up removing my K&N and just cutting a hole in the stock air box to increase the airflow. It worked in my opinion just as well as the FIPK and there was no noticeable change in exhaust tone.

I've looked at the H2 K&N kits and though I'm tempted I think I'm just going to save myself the money cut a hole in the stocker instead. This assuming the stock box has the usual tiny a$$ holes as everything else I've seen.

 

I talked to my Hummer dealer and they say the intake wont void the warranty.

I have to say you can hear the set up sucking in air, but in my humble opinion, thats the coolness factor kicking in. Who would not want to hear their engine gaining more power while driving? Thats just soooo cool to me and even if I did not get a HP increase, its still way cool to hear it.

 

Yep, but I thought that was about it too. Sounded real good with the hood up and listening to it but did very little for exhaust note. As far as HP goes .. yep, I thought it added a little and definitely looked good (I had the chrome version) doing it. Personally I'm rather sick of "gaining a little" horse power wise. I drove a RAM SRT-10 (8.1L V10 Viper engine) for about 2 years as a (summer) daily driver and every time that thing took a breath it was 3 bucks worth of gas LOL! In comparison my H2 is an economy vehicle hehehe. It was fun though, I'll admit that!
I guess here in my umm .. older days I'm just as happy with the stock performance of the H2 as I was blasting down a straight piece of road at 120+ with a Porsche trying to keep up hehehehe ....