I'm quite pleased with Thorn because the sounds it produces are fairly different from all the other synths I have. And, as such, it inspires me to write different music. It's definitely not a general purpose synth (which is fine b/c I have many of those). I would describe it as an ear-candy synth. I also really like the GUI; it's very intuitive to use and provides a ton of control (and is quite large!). Bottom line, I'm very glad I bought it.
And everything I wrote above about Thorn applies to LION which I also own, is also unique, and is another ear-candy synth that I would not use on every mix but is nonetheless very inspiring.
In contrast, I do not own (nor do I plan to ever buy) bx_oberhausen b/c, to my ears, it's a generic synth and would be redundant in my collection.