Funny thing is I used to think that discrete was on its way out about 5 years ago.
But suddenly Vista came out and the audio was no longer hardware accelerated. Which meant that the driver software actually mattered a lot more. Companies like Realtek made shit software and couldn't keep up. I had 3 boards with Realtek chips in them, and as of the beginning of 2010, none of them had proper driver support for Vista and 7. Channels were frequently missing, wrong frequency range was sent to speakers, none of the dsp worked as they should... The difference was very clearly audible when you switch to XP.
So yeah, unless you invest in more expensive motherboards with proper onboard audio with good driver support, you'll want dedicated.