Windows 7 Remote Desktop host capabilities

I currently use the XP pro feature ?Ask a friend to help you? to provide help.
I have discovered that:
XP to XP works well.
XP to Vista works.
Vista to XP will not work.

Before I invest in Windows 7 I would like to know:

What are the capabilities of ?Windows 7 Professional? to ?Ask a friend to help you??
XP to 7 pro?
Vista to pro?
7 Pro to 7 pro?