[XeTeX] XeLaTeX, polyglossia, babel, hyperref, fontspec, ...

[TeXWorld]

Hello,

I'm a latex user. I 'm also trying to use xelatex and I must say that 
I'm quite satisfied.
I'd like to know several things :

1/ Can I continue using babel (with french option) without problem or 
should I use polyglossia ?
Is Polyglossia as powerful as babel ?

2/ I have always been told to load babel and hyperref packages at the 
end of preamble. What about xlxtra and fontspec and polyglossia ? Should 
I load them before or after babel or hyperref ?

Thank you


Jack