Want to see who you're talking to over your IM? You may want to use iChat or Skype, but now, Google Talk can support voice and IM chat. You can find out more.
For those who are dependent on Skype (and perhaps 3-5% of my friends actually use the service consistently), it's nice to know that Gmail will probably fill the void for the remaining 95-97%. Many forum members found that Skype's functionality was limited (you needed XP SP2, for example), so the Gmail solution should work pretty well.
That said, the actual integration of these new features hasn't come without its criticisms. One person expressed his disappointment that Google has not installed a folders system and he considers that important. (I see the point and I agree that Labels alone are NOT the suitable replacement. A future Gmail Labs feature, perhaps?) Other tweaks have been requested within Gmail that would make the *mail* experience a more productive one.