Hi Salva - We've de-activated Multi-Inventory without having used it. I don't know if we're eligible for any refund, but thought I would at least tell you why. Perhaps a future version can incorporate ease-of-use improvements.
We are a small manufacturer shipping products from two locations. Each location has its own inventory of raw materials, product parts that form the BOMs of each of our products. When an order comes in through website, we fulfill it from either (not both) locations. We have custom order statuses set up like "Todd has it" or "Cheryl has it." Ideally, when we apply those order statuses, ALL of the BOM elements for every one of the products on the order will be deducted from either Todd's or Cheryl's inventory. One click after properly set up.
As Multi-inventory now stands, fulfilling an order with appropriate stock control for each location involves expanding the BOM tree of every product on the order, and indicating manually from which inventory the materials should be decremented. This can easily be dozens of clicks. For every order. It's just not worth that headache for us.
What we have decided to do is just make a spreadsheet of the few dozen BOM elements that take us more than a short time to resupply, and track our inventories of same manually at each location once a month or so, so we can order hard-to-get parts in time without running out, rush global shipping etc as has been the case over the last 4 years of business. It's still more manual accounting than we'd prefer, but less than being forced to indicate which inventory gets hit for every last BOM element of every product in every order, as ATUM MI seems now to require.
There's a chance that I have missed some easy workflow optimization, but when presenting the proposed new workflow to my business partner, she balked at even having to change the order status to pending/on hold and save. Just that. Then when I began to click open the BOM trees of every product on the order, she just laughed and said "no way." She hates even looking in Woo at all. She wants to fulfill orders 100% in Shipstation, which for all its faults is a little faster than most equivalent shipping operations in Woo.