I agree that Captivate's display is not as sharp as iPhone's. In fact nobody disputes that. The importance of this however is another matter. The normal text is pretty sharp. The pixelation becomes noticeable only when text size gets very small. One probably should not read anything using this small font anyways

Also while the text may not look as good as on iPhone (again only for very small fonts), does it really matter? Due to our cognitive abilities, we can read this text just as easily as the better text on the iPhone so it becomes mostly the matter of aesthetic. On the other hand, SAMOLED screen has much better contrast and richer colors so it looks much better when viewing videos or pictures. One can say that iPhone screen is better for text whilst SAMOLED is better for video and pictures.
Add to this the following advantages:
a. the screen is thinner - hence:
1. No need to compromise phone thickness for external antennas
2. More space for battery
3. Phone is lighter
b. SAMOLED consumes much less power -> better battery life
c. Bigger size - lots of advantages here
d. Real Gorilla Glass (from Corning)