like it it's a good idea
I've found on other forums that they some times have a newbie section
this a place where they can introduce them selves and talk a little bit about whatever they want
where the live, what there interests are,
the welcome letter is a good idea make them feel part of the family also you could provide a link in the letter to where they can make the 1 post
I know from when I first join the forum, I found it quite hard to find my 1st hello post as the site can move very quickly during the week and being a bit of a computer virgin at the time didn't fully understand how all the function worked on the site
the thing I've found on other forum with this section is that people become more involved quicker as they can build up a relationship with members who choose to answer the post, it also helps that they can also see who is new to the forum so they feel less alone/imitated from/by the other older members, plus the post doesn't get lost in all the other random posts
my 2 pence