I don't own one. I did try one a few times. My use was very limited, 2 knives offered by the owner and my SAK. This was in two different sessions.
My SAK it dulled from what I felt was less than optimal.My SAK was in need of a touchup. The Vulkanus made it require a full sharpening. The other two knives were in such a state that it did help. But then a brick would have helped these knives. Maybe I expected too much during my limited use. I can't recommend it.
There are only 2 systems I do recommend. If you are looking for relative ease of use for the new comer to sharpening at the lowest price. Get a Sharpmaker. They work. The learning curve isn't that great. Practice and patience with the SharpMaker (as with any sharpening method/system) does yield great edges.
The other system is the EdgePro - Apex. It's more money wise but in my opinion worth it. The training/learning curve isn't that great. It will give you the ultimate in sharp. It is more versatile than the SharpMaker. It is more expensive but not all that much if you factor in additonal rods for the SharpMaker.
Personally I've owned more "gizmo's and gagets" (which I put the Boker Vulkanus into) than I care to think of. Multiple hundreds of dollars over the years. I got my EdgePro - Professional model and I've never thought twice about the money spent. The Apex is the consumer model, the Professional is just that intended for the Professional, high volume, or dedicated home user. roughly 3 or 4 times the price of the Apex. The Apex may be the most bang for the buck where sharpeners are concerned.
SharpMaker runs 75$ and up depending on what rods you add. The only down sides to the Sharpmaker- 2 pre-set angles. Major reprofiling can take a LONG time. Stones tend to load.
The Edge Pro Apex starts out in the 125$-$180$ range. With a full range of stones. Downsides there aren't any... Ok being picky. Some people have issues with the mess. (set your Apex in a large glass baking pan, Lasagna size, and no mess) The EdgePro shuffle from hand to hand may be awkward at first. (I have heard of 3 people who never could get used to it)
The EdgePro - Professional (only available direct from EdgePro) fully loaded is 485$ the scissors attachment is another 95$. In my opinion worth the money.
This is the ultimate in sharpening "systems". Expensive but you get what you pay for and then some.
I own both the SharpMaker and the EdgePro-Professional plus a lot of other sharpening items. If I had to have only one sharpener and I was only doing knives I'd buy the EdgePro Apex. It may be the most under rated system out there. The SharpMaker is second on my list.
Personally I say get both. Strongest recommendation is for the EdgePro. Followed by the SharpMaker. A very distant 3rd is the Razor Edge guide and stones. Hope this helps you narrow your search.