I got to play for quite a long time with the Samsung Omnia, the iPhone-Killer wannabe with Windows Mobile 6.1 Professional, here at IFA 2008. The verdict: it's not an iPhone killer, despite previous demos. In fact, it sucks. It has a poorly designed interface, lousy response time, buggy software, and it felt cheap and fat on my hand. I even thought that I was being even more thick than usual while trying it, but I got the Omnia expert lady to give it a marketdrone spin for me and her last sentence summarised it all: "Oh, naw it'z not verking at all. I think I haf too many tasks open. Sorry."
The Good: It has Windows Mobile 6.1 Professional, if that's your thing.
The Bad: All the rest. It felt slow and buggy. I found the stuttering interface particularly bad. The side bar widgets, which need to be dragged and dropped onto the screen to make them appear as tiny little programs, is an atrocious, gimmicky interface design. Wastes space and requires a motion that is simply not needed. Samsung designers should learn that a telephone is not a desktop computer, and replicating the Mac OS X Dashboard doesn't work in a tiny screen at all.
Bottom line: After 45 minutes poking and getting frustrated by it, my verdict is to avoid it like the pest. As a consumer, my first impression is clearly one of horror and frustration. I would rather get an HTC. Or a Sony. Or a Nokia.