I talk a little about Palringo in Phandroid Podcast #4 that'll be out soon (if not now, by the time you read this)...and from my impression, a very, very slick app that has some serious coverage in terms of network support. One thing that I did complain about in the podcast was the fact that I couldn't find a "settings" page where I could turn on vibration for new messages. I love being able to be logged onto IM all day on my phone, and when someone wants to talk to me they can IM me and I have it...but if I don't get a notification, then I won't check my phone as often. Other than that, an extremely well-thought-out application.
One way that it differs from the otherwise excellent web-bases services that are geared towards mobiles (such as Meebo), is that it is inherently faster and (hopefully) is able to access the phones inner data to provide more functionality. This app definitely has potential to be the most full-featured IM app on the Market.
Just my .02, of course