What version of Android should I develop for? -

Just started to develop Android, this idea is to create an app available in the AdWords market. I would like to be able to use bulit in "Graphical Layout" (WYSIWYG) to create UI. Now I have two questions:

1. I can see that almost all users Currently using Android version 2.2 or earlier. What I think, the 3.0 version has a lot of improvements, especially when UI creates, but when will the 3.0 version be available on a large scale? Should I develop for 2.X users or should I go with 3.0?

2. Do you recommend using "graphical layout" to create a UI or what should I do manually using XML-files? I have read that "graphical layout" was not working well in the first version, but better for 3.0?

   current data 2.2 on Microsoft, 2.1% on 2%, 2.3% At 1%, 1.6% to 1.6%, 5% is at 1.5%. > With 2.1+, you can reach 88% of the market. 3.0 is for sure about the future, but is only available for tablets - especially for all its development mobile phones will be left for a long time.

   Graphical layout editors get better and better - I did not have much luck when I saw them 9 months ago, but the situation has changed.

   I propose to consider and use them - and then a) look at the results and optimize the results if you do not want to have a graphical editor.