I’m using Nimbuzz all day at the moment from my Nokia E90 to help me stay connected across Skype and every other IM service I use (Gtalk, MSN, Yahoo and so on).
The Skype calling integration is a piece of genius. Try it out. It works very similar to the 3UK Skypephone or their X-Series Skype offering (that is, the application initiates a call to a local number in your geographic territory, so that cost comes out of your bundled minutes — and connects you to the other party via a VOIP connection). Works brilliantly.
There’s also a file library feature that I haven’t yet played with. Loving it. I’d appreciate your perspective.