We got ours taken about a month after we got engaged and 5 months before the wedding since we wanted them taken at the beach and didn't want to be miserably hot when getting the photos done. It was just me, my fiance and my sister on the beach in March. At first the pictures were awkward because while my sister is a talented photographer - she's not a professional and we weren't really sure quite what poses to do and etc. But after like 20 minutes, my fiance and I quit worrying about posing and just started playing and spending time together. Those are my FAVORITE pictures from our engagement set! When I put our pictures up on Facebook all my friends wanted to know who my photographer was and how much s/he charged. It was great! I've always loved our engagement photos even though my hair frizzed up halfway through the day (it may have been March, but it was still the beach in Alabama - the humidity will still strike! lol!).
As for using them - like I said, I put 120 of the 600 on Facebook for everyone to "ooh" and "ahh" over. I also incorporated many of them into photo albums for the wedding reception. But one of my favorite things was our wedding invitation! www.facebook.com/photo.php?pid=32337387&l=
But always remember - this is your big day! You get to do things your way!