Simplicity, ease of use, and playing the widest variety of file extensions are what give any free, open-source media player the edge. While the AVI Player app is definitely not the only multiformat media player available, it is specifically designed to make AVI files directly accessible on your smartphone.
The AVI Player app offers a single menu through which to access available files. There is no welcome page and the interface does not have a front end. You just need to select any AVI file to play it. We used a slightly older Android 2.2 phone in our tests and, overall, the files worked pretty well and were read and accessed completely. However, we immediately noticed that the app lags a bit as the file plays. We initially thought that it was due to our test unit, but after installing the app on another device, we found that the problem may arise from the app itself. We didn't of course directly tinker with the app inside, but our guess would be that there are compatibility problems with some of its audio and video data streams.
As an app capable of directly playing AVI files on your smartphone, AVI Player does its job. However, with the availability of general-purpose media player apps in the Google Play Store, its practical use nowadays is very limited.