Aside from the aesthetics of the thing, I don't see a lot of difference between the Thalia and a Kyser. Both use a lever to allow one-hand deployment, and both deliver a set tension via a helical spring. Those of us who dislike the Kyser one-tension-fits-all approach will dislike the Thalia. Myself, I abandoned my old Hamilton lever-and-spring capo as soon as Shubbs appeared.
The Thalias are certainly pretty, though.