I use to love using Outlook and replied on it to manage my business for follow-up, appointments, search, etc. When you get as much mail as I do, you need a good mail program.
I had to stop using it and now only check my email with a web based (yahoo) email. I pay for this.
I just got sick of watching Norton pop-up all the time with viruses it couldn't fix. Not only that it really slows your work down when it's checking every email you're sending as well as receiving.
On top of that you have a personal firewall and 100 things going on at one time.