I am not a Skype user myself but I know many people who use it religiously. Last time I checked it was one of the biggest long distance carriers worldwide. RIM & Skype have yet to release a decent Skype client so Shape Services IM+ for Skype is the next best thing. It lets you chat with your Skype clients from your BlackBerry without all of the extras found in the full IM+ All In One Messenger.
The IM+ for Skype version 4 also adds the push to talk (walkie talkie) like VoIP calling over Wi-Fi using your Skype account. So far this is pretty limited but shows promise if Shape can figure out how to make the calls full duplex instead of half duplex.