i was a d2 owner and switched to the touch 1g. now i have the touch 2g. both the d2 and the touch are nice players but they really need to be used for what they are to be worthwhile.
for instance, i thought i would listen to fm radio when out and about and did not, so the fm function never got used. i also thought i would do line-in recordings but... the wma recording of the d2 was wasted as i don't use a windows computer and record losslessly (so i use my sony 828). i also wanted gapless playback and the d2 does not do that.
what it does is good battery and size and has great points for versatility. it is not a good video player as the screen really is too small to be viewed comfortably. its codec support is okay, but with no aac, it is really annoying.
the touch has no fm radio which, though i don't peruse, i wish it had. it does have gapless and aac which is nice. videos are better but... not great. the screen is big enough but not of high quality compared to some other players i have used.
as for lyrics: never used.
buildquality. it depends. if you like all plastic, then the d2 is your bet. if you like metal and glass, then the ipod is your game. it is made of two pieces of material wedged together and is very sturdy. the d2 for what it is made from, is also quite good.
sound: that is up to you as well. the d2 has typical to slightly heavy loss in bass response with low imp earphones (up to 50 maybe even 75 ohm) so can sound thumpy rather than well resolved. without eq, its frequency response is slightly peaked in the treble which makes it sound detailed.
the touch 1g is more laid back and has the most hiss of all three. while i really liked its sound, the 2g is easier to listen to and has the least hiss of the three. the apple products to not have a usable eq while the cowon has a decent bbe effector and okay eq machine.
sq: again, up to you. technically, the ipod is superior, but you may like the sound of the d2 - i did not. i need gapless, aac and a detailed bass and good left to right separation. as you can see though, many love the cowon d2.
battery life: both are great. my touch 2g gets at least 30 hours, i have no idea how much for music alone though. my 1g got around 25-28 on average on a battery rated for 22 hours. the touch 2g is rated for 36, so i expect 40.
my d2 got 35-45 hours without using the sdhc. they are pretty even i think.