not many people seem to be aware of (or just haven't tried) WebMessenger as an alternative. It's free and has been in the appstore for a few weeks now. v1.0 was a bit unstable, especially on 2.0.2, but has been working pretty well for me since upgrading to 2.1. And they've just released v1.1 which improves a number of things. I've been testing it out, and ok, it doesn't keep you logged on when you leave the app which I know will be a show stopper for some, but it does retain the last 10 messages in a conversation, and it also delivers any messages that were sent while you were offline. I've tested with Google Talk accounts by simply closing and reopening the app, and also by rebooting the iphone, sending messages from my wife's gtalk account, and the messages were there waiting in the conversation when I reopened the app.
I prefer this app to palringo, as it's much simpler (and nicer imo) GUI, and obviously more stable than MC!
I may buy Beejive when it comes out, providing I read some good reviews and it warrants the cost, but I'd recommend this as an alternative that has worked well for me.