nos402 said:

What are the various formats? There's talk of the 15GB MKV, AVCHD, DVD5. What are the differences?

MKV: currently the best-quality version. Can be remuxed into a Blu-ray, or played as-is. I don't believe an MKV version of 2.1 is planned (see below).

AVCHD: mid-quality, can be burned to a DVD9 and played back in many Blu-ray players. This format is good for people with Blu-ray players, but without Blu-ray burners.

DVD5: lowest quality, also contains only one soundtrack option (English 5.1). However, this burns to a DVD5 and can be played back on any DVD player, which makes it a good "friends and family" edition.

Harmy also plans to release a Blu-ray version (highest quality with tons of extras) which can be burned to Blu-ray, and a standalone M2TS which is the same highest quality and functionally pretty much just like the MKV.