iPhone - is it a good tool for traveling business people?

Although I like the form factor and user interface of the iPhone, I increasingly question its use as a tool for traveling business people. In no particular order, there are some of the concerns I have about the device and AT&T's service.

• My work involves travel. I need to be able to rely on a smartphone's ability to be an internet tablet, a Email client and, oh yes, a telephone. AT&T's network in Boston, New York, Orlando and San Francisco often left me with poor telephone service, poor internet access or no access at all.  Colleagues using other networks often had no problems whatsoever in the same locations.
• International roaming is unbelievably expensive. Since the iPhone is locked to AT&T's network, I can't purchase a low-cost SIM and pay as you go service in another country.
• The calendar handles events scheduled in different time zones very poorly.  Even though many business travelers fly to appointments in other cities, the iPhone calendar offers no way to enter an event that starts in one time zone and ends in another. In fact, there appears to be no way to enter the time zone of an event on the iPhone itself short of changing the default time zone for the entire calendar. There are ways, however, to tag events with a time zone on a host PC or Mac.
• The Email client doesn't recognize meeting invitations. The client doesn't even offer a way to look at those invitations.  Once again, the only way to deal with these typical business situations is head back to the host PC or Mac.
• The Email client has no ability to create or delete folders. Once again, the only way to deal with this requirement is to head back to the host PC or Mac
• No multitasking. Need I say more?
• Apple's cat and mouse game with developers making needed applications, application features and the like unavailable.
• AT&T where is support for tethering?

I'm increasingly finding the iPhone to be a poor tool for business people and am seeking a replacement.  I'll let you know what I find.