I didn't follow the link. However, I'd like to try and clear up some things.
The state being save isn't your appliction's code state. Its the state that faces retains. You need to read the chapter on this in whichever book you have (buy a book, if you have not. JSF in Action or the O'reilly book I'd recommend). Basically, jsf builds its own interface components, and these bind to values and functions on your objects. When it saves state, its saving its own objects' state. Your objects' state is up to you. If you use session scope, your objects stick around, but you need to be careful with sessions.
As for benefit of client vs. server, there's no clear winner. If there were, there would probably be only one option.
Session: keeps state on server, which reduces network traffic and processing when rebuilding state. Can't use back button, and when developing you can run into some strange issues.
Client: Can use the back button. A little more consistant for development. Increases network traffic to write state to client, and processing when submitted.
Personally, I use client state. This is due entirely to the back button issue. In version 1.2, there is supposed to be some better back button support. I haven't read much on this, but I think it only keeps your app consistant. It doesn't actually make the back button 'work' with server state. For internal applications I might wind up using server, as I can dictate how the application is used. For external applications, I'd probably go with client. Its hard to tell customers that they can't use a back button or refresh. Imagine Dell telling you can only use your new computer's mouse on Tuesday's. Its not that bad, but its not the best conversation.
We got into a performance discussion when talking about this not too long ago. I think that if you're building an app for huge numbers of concurrent users, or a big public site, and your screens are going to be critical path, JSF might not be the best thing for you. For the other 99.99% of applications out there, some performance hit might be eclipsed by the development time savings.
However, the jury is still out as to if you'll be more productive with JSF. I'm still figuring that out...