MSC vs MTP / WMF vs MP3 / firmware update or not?

Hello everyone,

I just ordered an m250 and have read all posts on the m250 forum, however I have 3 basic questions before I start using my m250:

  1. MSC or MTP mode?  

         From the posts that I have read it seems that most users prefer using MSC mode.  Is this correct?
         (I read that files loaded with MTP would not be visible in MSC, so seems best to start out in mode you will end up using).

  1. FIRMWARE UPDATE, OR NOT?   

       Some of the posts have indicated that once people updated their firmware, they regretted it.
       Would you recommend my doing the firmware update before using the device?

  1. WMF  versus  MP3  file formats?
            Since I will be starting from scratch, seems would be best to decide on which format I will use.
            Which do you recommend?

Thanks for your advice, and for this great forum.