There are many advantages to merging in Word 2003, but there are also parts
that now take much more time.  Previously, one could easily select a merge
field on the fly, while creating the document.  I could quickly add
punctuation, spacing, partial sentences, etc.  Now I am out of the document
when I select the merge fields to be incorporated.  It takes several extra
keystrokes to insert a variety of fields, especially if the fields are being
inserted into the text of the document.  

I have been a heavy user of mail merging for 15 years, and find this to be a
step backward.