Afaik the iPhone is simulated not emulated, the binary is built for x86. So I doubt it would be too slow -- certainly not slower than the device itself.
Now that I think of it, I've tried it on a machine with an AMD processor which was 2Ghz (don't remember the exact model) but it hadn't SSE3 support. SSE3 instructions are emulated on OSX86 which makes it inherently slower. And on my 2Ghz machine with 2Gb of ram the emulator was in fact slower than the device itself.
The Intel Atom has support for SSE3 instructions so it should work better but I believe the stability problems are still there.
Intriguing you would find it slower, I guess it is possible that the binaries are built to the baseline Mac architecture requiring some instructions to be emulated via invalid instruction exception on lower instr sets, which may also explain some of your other stability issues.
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.
