If email is the most important...or the only important thing to you, Blackberry does email better than most. You can dress up a Blackberry with chrome sides, trackballs, blue & red plastic...and all that, but in the end...it's still a Blackberry, and if you want a phone that does anything else well besides email...there are better choices.
Having had the Samsung Blackjack and the Palm Treo 750 for a while...I can say with conviction that I hate the Windows Mobile OS with a passion...although I must say that Samsung does a pretty good job of it...much better than the Treo. The Treo 750 is the Treo that most people love to hate...with a huge number of glitches and issues, most of which have been around from the first release day...and have never been resolved.
I have had the Treo 680, with the tried and true Palm OS for several months of daily use and love it. It has an amazing support umbrella online...since the Palm OS has been around for a long time. And, although the phone has some quirks...like any other, they are easy to work around and are few compared to the 750 and other smartphones. The phone is easily modified with hundreds of 3rd-party software apps that can be quickly downloaded...to make your Treo 680 whatever you want it to be, and do pretty much anything yuo want it to do.
I was totally intimidated by the prospect of a steep learning curve going from regular mobile phones to a smartphone...but the Treo 680 has made that minimal at the very worst. I cannot say that at all about the Treo 750 and the Windows Mobile OS. It is a bear to learn...and hard to enjoy.
For a "grown-up phone" that is also good looking...the Treo 680!!