The concern goes with both iOS & Android, and both Alloy & JS generation.
Generally the attribute of top & left is quite reliable. However I can't get attribute of bottom & right to work as expected. Also on iOS, "center" attribute of Label works but no effect in Android. Usually I need to calculate the sizes of View Label, then use "left" & "top" to simulate.
I found this for several Ti version releases. Any clue?