Definitely worth buying if you plan on actively playing Unturned. Not only do you get access to cool stuff, you also support the creator a lot with this.
To show what BIG difference the gold mode can make, here's a summary of my first day with it on:
-Found a humvee that was in perfect condition
-Never had to make a canteen, it spawned and enough food to survive forever (unless you're lazy, get out there and loot the towns)
-Found military grade weaponry, even a timberwolf (Strongest rifle in the game)
-Found a ghillie suit
-Managed to fortify a place for myself in 5 ingame days, wire fences, electric traps, most of which were found.
The boosted loot feature, is an EXTREME advantage. You'll be finding so much loot, you'll have to do multiple trips or get your friends to get gold too so you can carry it all together.
And the double XP thing, I managed to max all skills in 24h. You can't do that without gold, unless you're a real hardcore player of this, then you've earned my respect.
In all, get this. Seriously, the extra stuff may be sweet, but helping the creator make this game even better is sweeter.