Hi Steve,
I am not a professional editor and just do videos for a fun hobby. I just received final cut studio 2 yesterday after trying to decide between CS4 PP and FCS2. I started with iMovie and Final Cut Express and wanted FCS2 for better color correction and the Motion app.
The biggest advantage of FCS2 for a non-professional is the loads of templates and royalty content available. There are dozens and dozens of sound effects and motion templates that easily allows you to make professional looking projects. Also, you get the three wheel color corrector with FCP and of course the app Color. By watching the tutorials that come with FCS2 you can create some pretty cool color effects right away.
If you are used to editing with Final Cut Express, you will have no problems with Final Cut Pro. There are several tutorials out there to get you through some of the more advanced features and the basic features are exactly the same.
To me, FCS2 is so much more fun to use than CS4 (I tried the trial). The log and transfer for my AVCHD footage actually helps me keep organized and the output looks great. I am now wanting to buy toast to burn high definition DVDs. Hopefully, this will be updated for FCS3.
I would highly recommend the suite. For me, it is much easier and intuitive to use than the CS4 suite. My two cents....