The official date hasn't been announced yet, but it's expected to air early 2012 in the UK. It's definitely airing in May 2012 in the US, but I don't feel like waiting that long, so I'll find a livestream when it airs or something.

I think post-production is ending some time this week. Then they'll be able to deliver the episodes to the BBC so the air date can be organized.
Jeremy Brett really is fantastic. His portrayal of SH was by far the most accurate (in terms of the books) out of any adaptation I've seen. I have to say, though, Mark Gatiss's Mycroft is definitely my favorite, even if it isn't that accurate.