At present only android and Apple OS are looking loke surviving. Android has the lead due to wider application and users.
I have Iphone 4,(before had 3GS), i love it and dont think am going to change to S2. I am waiting for Iphone 5.
Many friends have bought S2, it is lovely and beats iphone in most of areas.
But
i think it is too big to use as phone.
Looks not as good as iphone.
build quality does not look good, u dont want color wearing of due to use after few months after paying such price, too much plastic.
screen display is excellent but resolution does not match iphone.
Rest of it is super.
problem with iphone is it needs time to master.
But it has class and status. Missing with samsung which u associate with TV, fridge AC etc.
My humble opinion, may be biased or maybe grapes are sour