I’ve been using a 50’ stainless coil for the last few years (3/8" though, not 1/2"), and it works fine. Before that, I had a 25’ copper coil which also worked fine.
At a different forum we compared the SS hydra to the coil I described above with differing water flows and temperatures. The performance difference was basically a wash. Which incidentally is harder to do with that mess of coils.
I have a copper hydra but want to eliminate that last piece of copper so I decided to just use my stainless HERMS coil. I begin the cooling with just cold tap and change out the water occasionally to about 100*F and then use ice + cold tap to hit pitch temp.
Yes, my first reaction to seeing the picture is that it would be hard to clean. It is interesting to hear that the two coils performed similarly, but I stand by my statement that surface area is important in addition to water flow.
Besides having a good flow of cooling water anything that increases the contact between the hot fluid and the cold improves heat transfer. Surface area of the coils can do that but also simply movement of the hot wort past the chilled coils is also quite effective.