I think I did test this version and the result was less than satisfactory. If memory serves, there was a lot of noise even when nothing was playing. Flashing the Lazy Jones fix firmware solved the problem. I can, however, also find Swinkels's 20120524 firmware in the same directory of my hard drive, so I might actually have accidentally flashed that one, believing it was the test firmware you mentioned (also present in the same folder of my hard drive). When I get the chance, I'll see if I can test the 20141027 test firmware a bit more and will report back here.
I have the Swinkels 20141027 version for a while and it also solves the issue with LazyJones, and also sounds better with 180... I have not noticed any problems.
To clarify this... This firmware works on some C64's and not others. On some machines, it works perfectly and has no noise, and on others it has all kinds of noise.
I have two 250469 Rev.4 boards - one has the problem and one doesn't.
I also have two 326298 boards - one has the problem and one doesn't.
All work fine with the CK lazy patched version.
I can't really pinpoint the difference, but it must be timing somewhere.