[XeTeX] upgrading Latin Modern fonts

[Alex Hamann]

There has been a couple of times where updated versions of Latin  
Modern fonts have been mentioned on this list. Indeed, the relevant  
archive on ctan is from early this year. I was wondering how  
important this update is, which would be the best way to install it  
and what benefits I can expect from this update.
  IIRC the lm fonts come with the tex distribution, right? Did gwtex  
or mactex also install the lm fonts I see in my  font book.app and is  
the latter linked to fonts installed inside the tex trees?
TIA,

Alex