I used the latest Outlook while it was in beta earlier this year - and to be quite honest.... I preferred it over the Windows Outlook. I find the Windows Outlook to be just insane with the number of buttons, and the placement of them is not always logical. I have no idea why they put the send button to the left of the to/cc addresses, other than they might have had a spot there.... most western eyes naturally flow left to right, top to bottom, then back to the top..... so the send button is the last place you would look for it when your flow has already taken you away from that location (first fill in to/cc/subject then body). There has got to be 30 buttons scattered around the mail all over the place - just full of clutter. After the beta, I decided not to buy (I have 2008 around somewhere - but don't use it anymore - I tend to use Pages/Numbers for personal, and LibreOffice for reading work documents since they are in that format).
Now the built in email client in OS X seems to work fine with the Exchange Server (webmail since I work at home) [a year ago it use to get stuck and not update after a while] -- which makes me happy since I really only want a simple email client. Most Outlook users that I have worked with only tend to use it for email as well -- nothing that the internal OS X email client won't handle.