i own a gf1 and i used lx3 before , if your primary is to make your background blur , object clear , gf1 with the 20MM pan cake lens is very very easy to achieve it . as for lx3 , you need to know the setting a bit as all the brothers and sisters mentioned ..
if budget is a matter for you , then take lx3 , it is a good cam ,
if size is a matter for you , then take S90 , take clear pictures but the blur effect that you wanted is not easy to achieve .
if die die want the blur effect , you can go for the gf1.
if you want something in between the price of gf1 and lx3, size and function , maybe Olympus pen can do it as well .
PS: when you can do blur effect by using gf1 , you will be wondering how to not make it blur yet the shot still steady ( because Auto mode tends to go to f1.7 in most situation ..)