The star button does nothing differently - it just lets you know that it is a new LED backlit version.
It can do the voice control or repeat last command like the older units depending how its coded.
You can get part no. 1T0 035 680C without an LED backlit screen - so make sure it has a star key so you know its the newest revision. The date should also be 2010... although there are some very late 2009 that have the star, and some early 2010 that dont!!
I've noticed a difference in 6.1 over 6.0 - the bypass beside my golf course doesn't exist in 6.0, but does in 6.1!!