Easily the best of the 3 DLC's IMO.
The gun (EMS pistol) is surprisingly pretty good, I can see some people not liking it though, It's a very versatile weapon capable of dropping enemies at all ranges and its charge shot deals a lot of damage if you can pull it off, it takes literally a second to charge up too. You can alternate between promary and secondary fire mid fire fight for some really interesting gunplay. It's pretty weak compared with the burst shot/hellshot but it has the quickest fire rate out of all the semi automatic weapons and this can make it useful in all situations if you can perfectly time those shots, it's very spammable too and can often be more reliable than weapons such as the plasma rifle. As a DLC weapon, it's important to note that it has it is very balanced as it is easily outmatched against a Vortex rifle/Hellshot but the flexibility it has is arguably the best in the game giving you more freedom to try differrent weapons, I reccommend the lightning gun as it helps finish enemies with low health at close range after being weakened by a charge shot. I also reccommend a tesla rocket to pile on more damage. If you like experimenting with differrent weapons and don't mind adding a challenging, yet rewarding weapon to your arsenal, this is it.
The Kinetic mine is excellent, especially in objective games where players are trying to defend points and capture flags, it's literally a free kill that requires zero effort, if you don't rely on frags/tesla's/siphons, this is a must have. It is pretty easy to destroy though and like the EMS, there are bette roptions available so it is balanced, it can be kinda annoying to be hit by one though. I reccommend using it alongside the Vortex rifle when shooting from afar as not only does it kill people whoa re approaching you from behind but it can also alert you when players are nearby.
The Robotic armor is cool, I like the piston set the most, makes you look really big and bulky, if that's your look then this is probably the best armor for you.
The hack modules are hit or miss but offer some interesting ones like hidden treasure, primal speed is handy in CTF games when you play flag carrier a lot and gun runner can also be pretty nice. The only one that sucks however is the one which rewards extra xp for glory kills, kinda useless if you don't use them which I don't plus it doesn't really add much to the gameplay.
The colours are all pearlescent, if you like mixed colours, it's got them
The patterns are a mixed bag, I like the carbon fiber and the hex one though the rest I really don't care much for.
There are some pretty nice taunts here, lots of dance ones but also the best taunt of them all "sips tea" emote.
And finally the real reason why you bought this DLC, the Harvester demon. The Harvester is easily the best demon in the game period, he has a reasonable health bar so he won't die easy but he's not too durable, still you won't be up close and personal with this guy, he is best used at long range. His main attack is basically the same as the lightning gun but the damage is multiplied by 10. The great thing about this is that it will hit anything that connects with it. You don't have to rely on your enemy's position, nor do you have to worry about putting yourself in compromising positions. The laser has a longer reach than the lightning gun, it is pretty much a gauss cannon really... ok, ok it's slightly weaker than the gauss cannon and considerably less range but you can barely tell the differrence, one beam and they're down.
I haven't even talked about the secondary attack and this is where the fun begins. Harvester, much like the Mancubus has a gauge that builds up allowing him to perform a secondary attack. Differrence is that the Harvester doesn't have to worry about overheating nor does he have to worry about enemies being on the ground, instead he shoots several energy balls in front of him in a cone dealing damage to anything around him (in front of him) in a semi circle, that means unless your enemy isn't behind you and they're in the same room, they're pretty much dead. Think of it as a slightly weaker version of the BFG (just a slightly lower radius with each ball).
It's also cool to note that the Harvester hovers around rather than walks, he can jump rather easily and escape dangerous situations easily but he isn't easily torn apart he has around 300 health which is pretty decent. If you are too worried about getting killed easy (i.e playing soul harvest and trying to stay alive for a long time) you might pick Mancubus over this but Harvester is so much more versitile and harder to hit so I would say Harvester is the best by far.
As for the maps, unless you plan on playing private matches with friends, I wouldn't spend your money on this for the maps because pretty much everyone has access to them now.
In case you are wondering the maps are Cataclysm (A half hell, half industrial map which is pretty cool and one of my favs, great for CTF and other objective games), Relic (a snowy map with an industrial feel, great map for FFA games) and finally Offering which is a dark and gloomy looking map which has a pretty nice aesthetic to it. All three maps are great and are easily the best maps out of all the other DLC's.
However you don't buy this for the maps, you buy this for the harvester, the EMS and the kinetic mine if you are looking to enhance your multiplayer experience. £12.00 may be pricy for such DLC but ultimately it depends on how much you're willing to invest in the multiplayer. If you like multiplayer and the harvester/kinetic mine seems right up your alley I'd say it's worth spending the money.
If you don't like the multiplayer and you aren't bothered about the fun little extras I'd stay away from this. Avoid the others too as they are all worse than this one.