If you have the usual 2+GB RAM I think it will work better. I've seen machines move from Vista to 7 and it was always better. HOWEVER if we had our number crunching app that took 2 hours, after the change, the number crunching still took 2 hours.
It doesn't change the machine that much but it can make the machine seem a lot better.
I am thinking about upgrading from Vista (came with my laptop in 2009) to Windows 8. Any opinions on whether that's a good idea? What are the differences? Will I see a big improvement in performance?