It seems like Nexus S will be another phone with a curved display (though different than Dell Venue). All OLED displays are different than LCD in many ways, but two of the big differences are that OLED displays are very thin, and they can also be bent, while an LCD has to stay flat to work. I don't know how useful this will prove to be in phones, other than giving them a more interesting and unique look, but I think we'll start to see more of them in the future.
Once Samsung completes their new manufacturing facility next year, which is supposed to have a capacity of up to 30 million smartphone displays per month, I'm sure they'll allow more manufacturers to use their displays then and they will definitely try to make even more interesting curved phones.
Until then we'll have the Nexus S with its curved displays and shape that seem to make it the perfect back-pocket phone.