This may be bold, but I think Microsoft combined with HTC has created a "Blackberry Killer."
I just installed Windows Mobile 6 on my T-mobile Dash. It's VERY impressive.
Your email is like your desktop Outlook. You can do instant searches, propose new times for meetings, see who the attendees are, look up people in your company directory. The form factor is tremendous.
Check out this video to see more (you only need the first few minutes)