5th ed Dungeon Masters Guide

Before splashing out nearly £30 for this, is it actually of any use within Roll20? How will it make playing on Roll20 any easier?

Its value is essentially confined to the DM's ability to call up the DMG's unique information inside the compendium. Is it worth it? Eh... I think you can pretty much live without it. I have it for those rare moments (e.g. how is cover calculated?), but if you have a hard copy near your computer, that should suffice. If you don't own *any* copy of the DMG, then it's potentially worth buying it inside of Roll20, but the vast majority of stuff you *need* is in the PHB. That's my two cents.

You get rollable tables as well as magic items you can drag and drop into character sheets as examples of things I use Do you need it? Probably not if you own the physical book and are happy to copy everything in. Does it add value within Roll20? For sure. I find myself looking more stuff up within the Roll20 compendium these days rather than having to use another browser tab to look things up and I've had players use the magic items with drag and drop. 

I doubted the DMG, but having had it in my compendium for a few weeks it keeps me from going to the shelf during prep. I would like to say it saves time, but it just frees time for more rabbit holing during prep...