One of the big differences we found between iOS and Android
development, is handling the multitude of screen sizes that come
with Android devices.
The Android solution to this has changed in Android 3.2. Prior
to this, different screen layouts could be specified for small
(~<4 inch), normal (~4 inch), large(~6 inch) and xlarge (~10
inch) screens. In Android 3.2, you can specify layouts based on dp
(density-independent pixel) units.
What we like most is that layouts can be specified for different
available screen widths, meaning that layouts can be
specified for different screen orientations. The YouTube app on the
GalaxyTab does this very well; in the portrait orientation, the
related videos section appears at the bottom, but when switched to
the landscape orientation, this section appears on the right,
making maximum use of the space available.
The android documentation contains detailed
information on screen support, including how to handle screens of
differing pixel densities.