The Kindle Fire HD's stereo sound is also tinny and a bit flat, even with the Dolby Digital Plus audio processing option enabled. And there's unmistakable distortion at maximum volume. Unlike the Nexus 7, there are no equalizer controls available. Still, the speakers sound better than those of the Nexus 7.
TV/stereo playback. The iPad Mini supports AirPlay streaming (if you have an Apple TV) as well as video-out via HDMI and VGA cables, so you can use it as a portable DVD and music player at hotels and other people's homes and as a presentation device at conferences and meetings via its video mirroring capability.
The other media tablets don't have wireless media streaming capabilities. Unlike most Android tablets, the Nexus 7 also lacks support for video-out cables. Fortunately, the Kindle Fire HD has a MiniHDMI port for the purpose. It worked just fine, both for playing videos on an HDTV and mirroring the Kindle Fire's screen.
Book reading. For reading books, Apple's iBooks and Amazon's Kindle apps are the best. Their default settings are the most readable, though you may want to increase the Kindle's default text size. I like iBooks 3.0's new scroll mode for reading -- turning virtual pages may remind you that you're reading a book, but scrolling is faster and a bit more natural. But after using an iPad with a Retina display, I noticed that text on the iPad Mini's non-Retina display was not as crisp -- yet it's roughly equivalent to the crispness of the Kindle Fire HD and Nexus 7, though they pack more pixels per square inch.
The Kindle Fire HD's reader and the Kindle app on the iPad both load pages fast, but the Kindle app exhibits noticeable lag on the Nexus 7. Also, the yellower color balance of the Kindle Fire HD's screen made the book pages dimmer and harder to read than on the Nexus 7 or iPad Mini.
On the Nexus 7, books in both the Kindle app and the native Play Books app were hard to read until I adjusted their text settings. With both apps I experienced a noticeable lag when I turned pages. On the iPad, Google's Play Books app is also slow, and it's harder to read there than on the Nexus 7, due to strange text display settings.
Magazine and newspaper reading. When it comes to magazines, the battle is between the iPad Mini and the Kindle Fire HD, both of which have fairly large magazine and newspaper subscription libraries available. Android's Play Market has a small magazine selection. iOS's Newsstand app conveniently puts all your subscriptions in one place, with the option to get alerts when new editions are available. The Nexus 7 and Kindle Fire also aggregate your subscriptions and offer new-issue notifications.