there isn't a huuuge difference between 4 and 5.  i downloaded 5 the other day and haven't used it much, but after playing around with content-aware-fill i realized it was definitely worth it just for that.  not having to crop a panorama and using content-aware-fill to create a bigger shot is awesome.  i love panoramas too.  and using content-aware-fill instead of clone stamp the dodging and burning a lot also is a huuge time saver.  i love CS5 so far.  definitely worth it in my eyes