my experience is that voip methods of communicating seemed like a great idea until i used them. strangely, it felt like a novelty and i quickly gave up using it - same applies to the people i was chatting with.
actually 'talking' to someone 'properly' certainly requires a great deal more effort than typing. you have to participate correctly in the conversation with all of the rules that come with it - trying to avoid embarrassing silences, trying to think of something actually worth saying, etc. the whole process just made me aware of what little is actually worth saying.
using irc or other text based communication allows you to just say what is necessary - it provides you with more time to formulate your reply without the 'listener' becoming bored by your long pauses - pauses of silence that would be deemed uncomfortable in a spoken conversation.