Well, to rest your mind a bit, Most of the Smartphones out there Including the iPhone cand do Over the Air Sync with an Exchange account and Sync your Mail, Contacta and Calender.
I Use an iPhone 3G with a Hosted Exchange account, and It works more or less flawlessly. You may need third party support if you get a blackberry and your Exchange server does not have Blackberry server installed.
Now on what phone to get .
Well the iPhone is definitely an option, as it covers the points you need , namely Phone, Mail and Web access. As long as the sites you need to access don’t use Flash, they should work fine. The main complain i’ve had is that the lack of multitasking and medicor battery life does mean that I need to either have an external battery pack with me or a charger nearby when ever possible.
If you do consider the iPhone, I’ll suggest waiting at least past Wednesday, 27/01/2010 as Apple has a big announcement and whicl its not very likely that the iPhone may be update its still a possibility. So it may be worth waiting a couple of days.
Another option is consider getting an Android phone. As far as I’m aware (As I currently don’t have one) all the android phones in the market support Exchange OTA sync, and have a webkit based browser, similar to the iPhones, so it should work pretty well. There are also some benefits with the newer 2.0 phones, especially if you use google services. Verizon had the Droid and Droid Eris and will be getting the Nexus One in the near future. T-Mobile has the Nexus One, which is currently the most advanced Android phone on the market, and has had pretty positive reviews.
If your Work Exchange server supports Blackberry enterprise Server, i’ll seriously suggest considering a blackberry. While the Os is not as polished as the iPhone or Android, it’s the best email machine I’ve seen. The keyboard is one of the best if not the best, and it does great job of handling mail and Calls. While the Built in Browser is currently not that great, an upgrade to a Webkit browser is expected soon to correct it. until Then Opera Minsi is available, which is a great browser.
You may also want to consider staying with WM, especially if you are used to it, though switching to a more powerful device like the HTC HD2. It has great specs and a great screen, and HTC has done a decent job of hiding the old WM Ui to a great extent. The advantage to this would be that all your programs would till work, while giving you much better performance and a improved browsing experience. Also the HD2 is also most likely to be upgraded to Windows Mobile 7 When it comes out a year or so down the line, so its pretty future proof.
While I am currently using an iPhone, I do on a daily basis get a little use of a WM phone (TYTN II) and a Blackberry, and each has its pluses and minuses. Best advice would be to go down to the store and try out the different models and see what seems to work for you.