Outlook
Recent versions of Outlook have a usability problem with their rules interface. When you get frequent messages from a certain address - like a daily or weekly subscription for example - you see them come into your inbox. After the first few times of moving them to a designated folder by hand, you decide you want to create a rule to do it for you automatically. You click rules, and there isn't an immediate way to create a rule that does what you need by default. There was a way to do this in Outlook 2000, and it even was smart enough that if you just created a folder, it defaulted to moving messages with the from address from the currently highlighted message into the most recently created folder. Very clever. With one click. On the newer versions, it wants you to create a new rule via a template or from scratch, which either way requires reveral more clicks. The most annoying thing is that when doing so, when you have to select the from address, it must already be in your address book or you have to type it into the field and you are stuck in a modal window. Since you typically don't have those from addresses in your book, you have to cancel out of the modal box, go to your inbox, select the message, bring up the address, copy it, go back to rules, start over creating a new rule, and paste the address.
Tsk, tsk, very poor. It should automatically default to the from address from your currently highlighted message, or not be modal so you don't have to cancel out to get to the address.
Another problem is that the buttons are very difficult to distinguish when you pop up Rules and Alerts, they looks just like text and you have to roll over to see they are a button. This makes something simple like "Run Rules Now" difficult to see. Another usability issue, and a step back from 2000.
IE has quite a few of these flaws, don't even get me started 
