On Orange Daytona (Ascend G510-0200), with no gapps installed: Tint browser (from f-droid.org) fails to display some images. Often, if you open an image in a new tab the thumbnail of the tab looks fine but the image itself looks all white, as if there was none. Often, "tiles" won't display or only a tile will. Zooming in and out changes which tile is affected depending in the zoom level.
Firefox (from f-droid) often causes the phone to reboot, aparently because it runs out of memory.
Streaming certain video files with firefox causes horizontal distortion (staircase effect) and wrong colors. They stream fine in Tint, and they play fine in FF if stored locally.
Firefox displays a black screen when trying to play YouTube videos, as if it expected the youtube app to take over, despite it never being installed.