Several years ago I did a few projects for the "Java cell phone" (J2ME) platform, and had a lot of fun with that.
After recently setting up NetBeans with the Java ME CDC tools and Eclipse with the most recent Android platform tools, late last night and early this morning I installed Apple's latest developer's tools that include the iPhone SDK and Dashcode. Since I very much like my Nokia N800, I am also interested in medium resolution devices (the N800 has a good 800x480 screen).
My interest is in writing web portals that support both browsers and small devices. One option is just creating special CSS for different web browser screen sizes, and another option is rendering page view data as XML or JSON and letting rich clients provide the display and handling of forms, etc. (an option I used several years ago on a customer project).
Ideally, I would like to be able to support a wide variety of small devices without a very large investment in my time getting (back) up to speed. I have just a little experience with Objective-C and Cocoa so for the iPhone, just using Dashcode looks like a good option (for me).