I've tried Tagspaces before, 4 or 5 months ago or so, and now look at it again (version 2.1.1, with W 8.1 64bits). My main gripe with it is the incredibly slow user interface. Apart from the fact that the listing of folders in the FolderViz. (what the heck is a 'FolderViz.???) is completely unusable as it is a cloud of thousands of elements which cannot all be displayed on one screen. It takes minutes before the folder is even shown, with only three flashing dots as feedback. And I've only one folder connected to tagspaces!
When I choose 'Show Files with this tag', it takes a LOT of time for the program to respond. This is wrong. I think the program should immediately acknowledge my request [yes, I see what you want and will now do my best to deliver] and give feedback about what's taking time (and preferably and indication of how much time). It would be a good thing if the developers of tagspaces would direct their attention to the UI.
This is a pity and I say this with regret as I do appreciate the need for recording metadata. And I like many aspects of the approach by tagspaces, such as the plugin architecture, the fact that it's cross platform. But the fact that the blog states performance is improved does not bode well for the future.