This might be concerned somewhat nitty picky :-) but wanted to know the importance of choosing an exchange org name so I'm not in a world of trouble later . Also, in particular since we are in a M&A phase several email forests will be migrated single forest new exchange 2010 org. I assume Ex Org names are used for internal and doesn't really matter what I decide to name it. How it suggested not to used the default, correct first Org? Thanks.

As long as you follow the requirements, the name isnt that important, but yes, choose something that will make sense and hopefully be future proof http://technet.microsoft.com/en-us/library/bb125143.aspx The Exchange organization name can contain only the following characters: A through Z a through z 0 through 9 Space (not leading or trailing) Hyphen or dash Note: The organization name can't contain more than 64 characters. The organization name can't be blank. If the organization name contains spaces, you must enclose it in quotation marks.