Wow, tough crowd today. Must be a Monday thing since yesterday was a day off for many folks.
I use GO all the time in scripts, especially migration scripts as they have a mix of functions, stored procs, and SQL statements including drop and create statements many of which must be at the start of a batch. Knowing where to put the GOs in the script make all the difference.
One thing about GO that wasn't apparant to me when I first started TSQL was that you couldn't use a local variable that was declared "across a GO". For instance this script gives you an error:
DECLARE @myvar varchar(100)
SET @myvar = 'Bob was here!'
In such a short script it's easy to fix, but in larger scripts that need to process in a specific order, this limitation may require using temporary tables or other objects to hold values from one batch to the next.