For an excellent Kurosawa and Mifune movie that doesn't involve Samurai, you absolutely must see "High and Low". That is one of their best. Too many people only associate them with Samurai films, but their non-Samurai films are actually way better. I also endorse the recommendation of "Ikiru". That is probably Kurosawa's greatest film.
This release of Criterion Collection films without extra features is directly analogous to their "Essential Art House" and "Eclipse" series sets, which also do not have extras, even though the films themselves are high-quality restorations. Criterion does this intentionally in order to make more great films available at lower prices, as well as to get films into the market sooner, whereas requiring the usual special edition releases for everything would result in too long delays.
If Criterion were to release these with all the extra features that you expect on a Blu-ray, they would be more expensive, and, as a further consideration, the market might not support that. People who truly want everything and who know what the Criterion Collection is will just buy the physical media. This is an alternative for those with less demanding needs.
