I have now been bashing away on MSN, AOL, ICQ using Fring
fring – Make free mobile calls, IM with Skype, MSN Messenger, ICQ, Google Talk™, SIP & Twitter, AIM® & Yahoo!™ and I think it is the most usable IM for Nokia's.
If an IM on your mobile uses the native ICQ, MSN, AOL protocols like your PC does, it kills your battery as it chatters frequently. Another problem is that the native IM protocols don't work well on mobiles and don't deal with the timeouts, bad coverage, receiving phone calls. Fring proxies all ICQ, MSN, SIP, AOL with its own protocol which overcomes these problems.
Another cool thing it is a full VOIP program so you can call any other Fring user directly over the net, you can phone MSN and ICQ users which have got voice setup.
The contacts directory integrates, email, gsm, phones, icq, msn ID's for everyone so it pretty slick to find someone and then decide if you are going to phone, or IM.