We switched to SW2008 a month or so after it was released, and it was quite a re-learning experience at first. I think we've got the hang of it now, but considering how radical it seemed compared to the old version, I don't think we'll be switching to 2009 right away.
Unlike some of you guys, we only ever use Solidworks internally, and only send PDFs out to suppliers. It doesn't really matter what version we use. The only reason we decided to switch to 2008 really was because of what new features there were available.
Mostly I use Layout Sketches to make sure that the components I plan to add to an assembly will have space to fit. For example: fitting power supply units into a chassis. It's a lot faster (and less taxing on your processor) to insert ready-made sketch blocks rather than inserting another assembly into it.