i actually think it's gotten a lot better from my ipod video to ipod touch 2nd gen and iphone 3G to iphone 4. really depends mostly on ur file bitrate, amp/dac (if ur using one), and headphones. sony, hifiman, sandisk, iriver have different components and eq options that enhance the sound but unless ur a serious audiophile, the difference is negligible imo. i was using an ALO RX with a LOD on my 5thGen iPod for a while. but then i realized my iphone didnt sound all that bad straight from the headphone jack. now my expensive headphones and amp are collecting dust. im just using decent denon earbuds and my iphone. good enough for my commute.
I will be hopefully. I'm having the ****tiest time with my iphone right now. **** won't sync. i want to back this **** up. damn steve jobs.