I've been enjoying the Cirrus Logic DAC since getting my iPod touch 2G two years ago. Won't be getting an iPhone 4 anytime soon (not allowed to as a foreigner in Korea), but I will definitely put myself on a list to get a 5th gen in Japan or Canada. The EQ fixed in iOS4 is huge - HUGE! and I've been enjoying it immensely with my iems.
I only wish its output impedance was as low as the Fuze or Clip. That way, every iem would play as flat as ever and considering the iPod/iPhone's good stereo image, it would probably take a very very expensive/nice portable amp to outdo the stock sound.