True, but the OS versions don't tell the whole story. Here's an example:
On stock android, creating a polygon with the paint style FILL_AND_STROKE will both fill the polygon and stoke the outside. On motoblur, it just strokes the polygon. On stock android, using FILL will render nothing if a polygon is rendered on a clipping boundary. On motoblur, it is displayed. Unless you actively test on different carrier roms, you will have lots of these little issues. For motoblur it isn't a huge deal since they make an emulator, but not all customizations are available as emulators.
I do both Android and iPhone development. There are some really nice things about Android, but the huge amount of fragmentation makes developing a polished UI very difficult.