I happened upon a Kindle Fire sale on QVC yesterday, and noticed during their repetitive hour-long demo that their Fire had a YouTube icon I'd never seen. A quick search turned up "
vTube- YouTube viewer & downloader(Kindle Tablet Edition)" a free ad-supported app at Amazon.
Although the App has a surprisingly large number of 1-star reviews I've actually been fairly happy with it so far. Unlike the official Google App you can sign in to your regular YouTube account and access your subscriptions. The interface is different than the YouTube default, but it takes very little time to get used to.
Aside from the somewhat intrusive advertising, I've noticed one big drawback. Despite what the description says there doesn't appear to a way to access playlists once you're inside a channel. If the channel you're looking at has several hundred videos it becomes a real chore to scroll through and search for the specific videos you want. This, to me, is a pretty significant problem.
Video playback is fine, and the app allows you to specify all the normal dpi settings that YouTube offers.
Overall, I like it, but the lack of useable playlists is a big drawback. Also upgrading to the version that actually allows downloads will cost you $1.99 or 199 coins.