I am hesitating to buy a sony FS 570, but I was in Fry's last week and they told me that the Fujitsu N3510 is much better than sony. I would really appreciate if you can give me some advices regarding this matter.
The sony FS line has some issues. I would advice you have a look at the sony forum to read some of the users experiences. + the new FS6xx will be released soon (hopefully those issues might be resolved)
But I would recommend Fujitsu anyway. If you go with fujitsu, I would recommend you order from www.portableone.com they have a free dual layer DVDRW upgrade + they offer one of the best customer service around. A lot of happy customers here, including me!