I don't consider myself as an audiphile, even with my current equipment I can't diferentiate a high quality sound file (eg. 96khz vs 44khz, 16bit vs 24bit), but I can hear the differences between a FLAC and an MP3, but it's really hard for me to identify what are those differences, it just sounds better, and I can hear them for longer.
For me, the macbook is too dark. It feels like the bass gets between everything else, If you have open back headphones they don't feel open, lower staging and imaging. While in the multibit, the bass is still there, more defined, probably equally strong but without interfering with everything else, I can hear music for longer with the multibit without getting tired. It's like comparing the bass from a movie theathre versus the bass from a tv.
The other big difference I notice is the quallity in the highs, and the rest of the spectrum, they are crispier but without feeling painful.
I also connected my speakers to the multibit, and I can finally listen to them without feeling anoyed. With everything else they used to feel cheap and like they were inside a box, now I can finally enjoy music and movies with them. (Audioengine A2)
But as MartinMan said, it depends what are you going to use for listening. I bough the Focal Clears last week, and I don't hear a big difference either. At least not the $500 investment in DAC and AMP.