The only place you're going to suffer with the S2 is using it as a music player. The Yamaha DAC is inferior to the Wolfson, you can't use Voodoo Control (though Neutron makes up for part of VC's functionality) and, in my experience, the audio quality isn't comparable to the original SG.
However, ICS is Amazon's first foray into allowing audio through the USB port. When the SG2 gets ICS, it's very possible we'll be able to use it with a battery-powered USB DAC. If that proves true, then I might well upgrade to an SG2 and use it with some $80 self-powered FiiO USB DAC/Amp.
I'd have wanted a Galaxy Nexus, but the sealed battery/SD card and inferior screen destroy the appeal of instant OS updates. Perhaps Samsung will rediscover audio quality with the GS3 and Apple's aggressive entry into Android's carrier markets.
Decent entry-level audio has always been a feature of the iPhone (and it can use external DACs like Cypher Lab's and Foster's as well). No reason for a hardware master like Samsung to suddenly miss out.
(You'll have to excuse me, because I'm a former full-time studio musician and, now that I'm part-time, I love the sound of the original Galaxy S when rooted with Voodoo and Neutron. I even listen to it with Shure SE535s when I'm stuck in a quiet place.)