I had some students that needed to merge two videos for a science video project. They then wanted to send the merged file to Youtube. I was going to try Imovie but together we looked at what we could do with Quicktime player in Lion.
All I needed to do was select “add clip to end” and the two clips are merged. Then from the share menu I could export the resulting video to Youtube.
I could also split the clip and select one of the split clips and insert a new clip before or after the selection. Also when you select Show Clips from the view menu you can drag and drop any clip you want into the clip viewer.
Real slick and gives you a way to make quick edits.