I've upgraded from the Dacmagic to the Plus. There is a large difference in sound. Plus has a wider soundstage and sounds much more natural to my ears. Sound is a bit lighter (less obvious mid bass), but also less brittle sounding with edgy recordings. That's why I don't understand the criticism of the Plus that's it's bright in WHF. They compare it to the Arcam r-Dac, which is a pretty stonking DAC, but, in my view, always sounds just a touch leaden and slow. Both the r-Dac and the DacMagic pPus have different sound signatures, so probably worth auditioning both if you care to consider buying either.
Now, anticipating a question about whether the Plus is worth £150 more than the vanilla DacMagic, that's much harder to answer. Put it this way - I still have my Dacmagic, which is now doing the business in my study, attached to my PC and an old Project Headbox II headphone amp. I thought I'd try the old Dacmagic back in the my hifi, as it would make sense to have the Plus connected to my PC, as I could make use of the new USB connection and 2.0 driver. That idea lasted about as long as it took me to get to the first chorus of 'Everywhere' on a 96khz FLAC of Fleetwood Mac's 'Tango In The Night'. After having listened to the Plus in my system since early December, going back to the old Dacmagic was just not an option. It just sounded so much more constrained, dull and artificial (and it's not at all). You pays your money...