How much can Android be customized?

view full story

http://androidforums.com – I'm about to buy Sony Ericsson's Xperia Mini Pro, but am not a big fan of the manufacturer's Android UI. The icons and other little elements make the interface look rather ugly to me. Can these be modified or changed? Are other things that manufacturers have changed about Android in their phones usually somehow locked so tightly that they can't be changed? For example let's take the home screen corner icon thingamajiggy. Can it be removed and replaced with a standard Android home screen? The Xperia Mini Pro would be my first smartphone, until now I only have been using Nokia's where muc (General)