I have a large store with many SKUs and variations. I also make use of many custom attributes.
Limitation:The only disappointment is that even the Pro version does not allow editing attributes.
To edit attributes, I go to edit button and add attribute to individual product. After adding an attribute and clicking save attribute, it is added to the product in WooCommerce, but is not displayed in Smart Manager, until you refresh the page.
Future scope: Wouldn't it be great if on clicking save attribute and closing the window, it displayed all the changes made by updating that product in the list.
PS: Please don't say... "this isn't the place to comment on Pro version"; you've already mentioned it in the description.