I'm guessing the cost and its "weirdness" aren't the reasons people are dismissive of Union. Soundspots' products are generally just not very good, sometimes being laughable. They're definitely cheap...but not just in the way you meant it.
With that said, I've never demoed Union so I can't comment on that specifically. But there was a time when I bought a bunch of Soundspot plugs 'cause they were so inexpensive and the GUIs were decent. I soon realized they were of subpar quality and haven't even demoed any since.
So I could be missing out on something amazing by not giving Union a chance...but I doubt it.