Beejive's already quite usable Beejive IM iPhone app just got an update to 2.0, adding file transfer and voice messages to its multitude of IM connectivity.
Currently, you can connect to "AIM, Google Talk, ICQ, Jabber, MSN/Live, Myspace IM, and Yahoo messenger" with Beejive. With 2.0, you can send in-line photos, audio and video files, PDFs and Office docs to anyone you're chatting with, provided the recipient has an IM client from the last 10 years.
The best part is the voice message feature, which you can activate with the microphone icon. The worst part is the price: $16. You do get what you pay for, and Beejive seems to be a pretty fancy IM app. [App Store via TUAW]