So if your Wii needs to be serviced (it's a reliable piece of hardware so the chances of it breaking down within the first 15 months is small but hey nothing is 100% perfect), Nintendo will fix it for free even if they see that you have Homebrew Channel installed?

If Nintendo would service a homebrewed Wii (provided it's within the 15 month warranty), I might get started with the homebrewing process today. I know it's compatible with the latest official Nintendo firmware (v4.2 or v4.3, can't remember where we are at) but I've heard that the newer sku Wiis are harder to homebrew than the older sku Wiis. I just have to figure out if my Wii is compatible. It's one of the newer skus (bought late March 2010). It's not the Wii Sports Resort bundle (The Wii, Wii Sports, Wii Sports Resort and WM Plus bundle) stock. I bought my Wii just before the Wii Sports Resort bundle came out (just my luck. lol. I was so pissed that I bought my WM Plus seperately while slightly later adopters got WM Plus and Wii Sports Resort for free).

Anecdotally, I've heard of people sending in their Wiis for servicing with the HBC installed. When they get it back, the homebrew channel is erased but covered under warranty. This is assuming the reason for sending it in is Nintendo's fault, and not something caused by you messing up a HBC install. If your Wii still turns on and you're worried about it, you could uninstall the HBC before sending it in for repairs. Not sure about current firmware compatibility, I did mine some time ago and haven't updated the FW since.

I'll PM a good link with a guide. Follow it to the letter and you'll be fine.