Though some of the Android consoles are interesting (the Shield certainly peaks my curiosity), none of them are worth buying for various reasons. These stem from a single issue commonly faced by Android; fragmentation.
A console is worth buying when it has a decent library of great games to play. And there are some pretty good Android games. However, most Android devices are phones and tablets, not consoles with a dedicated controller, so games are built with the former in mind. As a result, titles usually don’t take advantage of physical controls and rely on rudimentary graphics any device built in the last few years can handle. The Shield, for example, is theoretically very powerful, but you’ll rarely see games make the most of its hardware.
Some options, like the Ouya, seek to solve this problem by using a customized version of the OS with a proprietary storefront. This means all games sold for the console will work with its hardware, but it also means a barrier exists between Ouya and other devices, limiting selection. Most developers will focus on the much larger Android market, then think of doing an Ouya port afterwards.
Great games will be hard to come by as long as fragmentation exists, and without great games there isn’t a reason to buy a console. To make matters worse, last-gen consoles are inexpensive and have larger libraries. The Wii can be had for $99, while the Xbox 360 and PS3 are $199 and $249, respectively. And while a new console game is $60, older titles are usually sold for $5 to $20 and can be found for even less used, further narrowing the price advantage Android alternatives like to brag about.
If you want a console that you can experiment with, or can serve as a curiosity, an Android console makes sense. If you just want to have fun playing games, however, you should stick with Nintendo, Microsoft and Sony.