I watched the Blu-ray of this one last night. It is a nice HD presentation. There are stray dust specks here and there, but it's mostly excellent looking. The sound is PCM 2.0 mono if I'm remembering right.
What a shame that Neville and Houston didn't do more Holmes adventures. They made a very viable team of sleuths.
I also agree that the PQ looks really good...I thought it was nifty / amusing that Mill Creek included a slipcover with the artwork. I guess this will the best blu ray we will get for A Study in Terror unless another label gets it like Indicator