Yes you will realize better speed opening/switching applications on your laptop.
Open the memory door on the bottom of your laptop. See if you have 1 stick of 2gb currently installed or 2 sticks of 1gb installed. If you have 2 sticks, then you need to get rid of both of them to upgrade. If you have 1 stick, then you could buy another 2gb stick so that you will have a total of 4gb memory.
Or you can replace both with 2 sticks of 4gb for a total of 8. You'll get the best bang for your buck if you go with 4gb. 8gb will be a little better than 4gb but not a whole lot.