~via BB (wap.pinstack.com)~
But it's not ~FREE~
I tested IM+, and others of the paid variety too. Never satisfied with any of them to use them. Plus, my AOL screen name is dot mac, and I could never sign in because it refuses to recognise symbols (myname@mac.com).
Jabber is the way of the future. If you are not hung up about "text only" chatting with all major networks in one client with one client list, then Google Talk for BlackBerry is the best way to go.
Text colour cannot be altered (one is red and the other blue), but typing is the same as any other BB app. Double space provides the period AND return provides the "send" function. (From what I remember, IM+ cannot do that, but I may be wrong.)
Does IM+ integrate into the message list? Does IM+ allow click-2- phone/email/SMS/MMS any of your contacts from directly within the app? Google Talk does.
Best of all, Google Talk is free!
Now, I have to admit, setting up a jabber account and porting all your contacts from various networks into jabber can be / will be a bit of a frustration for a noob. However, the reward is the outcome!
There are some really good tutorials on getting on Google Talk and setting it up. (I don't have access to it right now because I'm on my BB, which is 7100 and slow.

I just test drove a 7130g demo...... I feel cheap coming back to my 7100r.)
If anyone wants pointers or has a question about setting up Google Talk, PIN me. I'd be happy to help out. I'm (nearly) an expert on doing it in Mac OS X Tiger.