I\'m using drawables like the following one for backgrounds with a gradient:
I believe that the screenshot bitdepth issue is a fault of 2 parties; Android DDMS/monitor as well as the device/emulator being captured.
If a device/emulator has a low bitdepth display, then there is nothing you do about that particular situation (GIGO). Although, I have clearly seen that on some devices/emulators, the screen capture quality that DDMS takes is lower than the actual display.
In my hunt, I have just found an application that I think solves this problem called "Android Screen Monitor" that you can obtain here:
http://code.google.com/p/android-screen-monitor/