I use Finale 2005. It's seems quite suitable for composing and arranging. What I don't like is my inability to create a divisi with differing rhythmic structures, and I'm also not fond of the percussion feedback that I often get. I do find it quite easy to use though.
I did get some feedback between the 2 programs from a professional composer. He made a comment that many of the composers who use Sibelius are of the pretentious variety. It seemed like an odd comment but is plausible considering brand identification.