Yea, the metal surround on the screen, and the case having a nice fit, and the buttons don't feel flimsy.
But mostly it's the "wow, I press stuff and I don't have to just believe that it's working on it". I was still considering a G300 before this came out, was the G300 somewhat laggy and slow?
The G300 suffered from it was 'almost' there, but not quite, it is a great phone, I am not a gamer, more Sat Nav, cardio trainer, browsing, Iplayer etc There are some great builds of Jelly Bean for the G300, but there are small niggles, where apps would FC, the camera was rubbish and the phone generally looked expensive, but felt very cheap, with creaks and groans when you held it.
Vodafone are charging £95 for the G300 and £130 for this, it is like chalk and cheese, this is miles faster, better built and has Jelly Bean, it's a no brainer.