First of all keep in mind version 2.2 is beta so it may not work 100% perfectly. Also, you will probably need to download the
Slow Processor version.
And yes, if you connect via Wi-Fi and call from your Skype to another person's Skype, there's no extra charge.
As a side note, you don't
need a Wi-Fi connection, many users use Skype over their EV-DO connections.