I came from a Pre to the Hero to the EVO also. I will say, for messaging there is nothing as nice as the way the Pre handles things. Yahoo, Google Talk, MSN, AIM, AND YOUR TEXT MESSAGES are all in one app. It's awesome.
But Android doesn't have anything like this - as far as I have searched for. Your text messages and your IMs are separated in different apps: you can get one app to handle both Yahoo and AIM, but your text messages will always be another beast entirely. This is one of my most missed things about the Pre, but this is made up for by Android's ability to do far much more than WebOS at this stage of the game.
As far as contacts go, I can tell you that the Yahoo IM app wants to add the info to your contacts - but I'm not sure about AIM.