I find Skype indispensable.  Skype has made it possible to live and work just about anywhere.  I use it constantly for voice, video, and chatting.

+ Easy to install
+ Usually just works
+ Free for computer-to-computer calls
+ Excellent call quality

– The interface has gotten more and more cluttered
– I have not found a decent way to connect my SIP phone to Skype.

One thing you MUST do before using skype is to modify the privacy settings, or you’ll be inundated by unwanted people trying to contact you for who knows what reason.

1) Options->Privacy

2) Make sure “people in my Contact list only” is checked for the 4 cases:
– Allow Calls From…
– Automatically receive video and screen sharing from…
– Show that I have video to…
– Allow IMs from…

How to get rid of the little adverts that appear in the bottom of Skype:

1) Options->Notifications

2) Click on Alerts & messages

3) Uncheck the two boxes “Help and Skype tips” and “Promotions”.

I also prefer the “Compact view”. From the main menu bar, choose View->Compact View.  This splits Skype into different windows.  One window for the contacts, and a window for each contact.