I can use it, because I have to for my day job, and many other job functions are tied into it. I have learned to live with it, but it annoys me constantly with its stupidity.
I have never actually used Outlook (went straight to Thunderbird when it came out), but a year ago a company wanted me to take a test for Excel, Word, and Outlook. scored 100 on first 2, and 93 on Outlook. Wasn’t too hard, but a little confusing at first.
First and last time I used it (thank God).