Saw Shada at the BFI on Saturday. Got the DVD, but had already pre-ordered the blu-ray.
In terms of quality, on the blu ray, they have upscaled the original 576i video rather than go back to the negatives and present the lot in 1080p. This was apparently a deliberate choice to maintain the look of the original show. That said, the studio based stuff (which would be most of this story) would have been shot on video rather than film, as UK TV companies mostly only used film for exterior and location shots (I say mostly as I believe some independant producers did shoot the entire programme on film).
The extras are HD, where available.
Anyhow, the story is excellent. Lalla Ward wasn't (unfortunately) present at the screening, but she sent a message saying that she always thought Shada was the most Douglas Adams-like Dr Who story, and having seen it, I agree. Oddly, the fact it looks crap almost adds to the enjoyment.