1) Support for iPhone and Android testing
2) Implementation of listeners - a much awaited feature
3) Better features for Ajax testing.
4) You can easily simulate clicking on front and back button of browser.
5) You can extract objects in bulk like QTP. For ex - extract all links of page. With RC this was a big hastle
6) Unlike RC you dont have to start a server in webdriver.
7) You can simulate movement of a mouse using selenium.
8 ) Tabs and pops are more or less the same. RC can also handle and Webdriver can also handle.
9) You can find coordinates of any object using Webdriver.
10) You have classes in Webdriver which help you to simulate key press events of keyboard.
11) Keywod driven framework is very easy to build in webdriver.