The Dell Mini 9 (which is Atom based) wouldn't be fast enough for the iPhone emulator (which you would use most of the time even if you own an iPhone). Moreover, Xcode on OSX86 kernels is unstable and buggy (first hand experience).
The Intel Atom has support for SSE3 instructions so it should work better but I believe the stability problems are still there.
But looking at your other comments I'm surmising your main contention is that one might just as well get a real Mac (eg Mini). I agree fully with this, imho the price difference is hardly worth the time to deal with all the various issues around install, upgrading etc.
I've also found the Mac mini to be completely adequate; and it still seems to me that even buying an iMac at $1k+ is still a pittance for a toolchain for this type of platform, considering one also gets a general-purpose computer to boot.
But there are issues with hackintoshes on Xcode. For instance I had problems with breakpoints (they were simply ignored).
Keep also in mind that you have to keep OSX updated to the latest version to work with the latest SDK releases. And some OSX updates update the EFI as well so there's the risk that you should have to wait for the patched EFI.
And you're developing an iPhone app? Maybe you don't keep up with the blogosphere, but I think XCode is the least of your worries...
Nonetheless, since then I've lost much of the initial motivation. So I know what you're talking about. Even though for me the reasons are more personal (and difficult to explain). I haven't had many problems with the whole publishing process though.