Good question. Google in particular does a great job of passing the link juice via 301's. I think there are several distinctions to be made here.
1) cross-domain 301's: They are helpful in site acquisitions, but after seeing dozens in the past year or so, I have some serious doubt about the authority being passed. Keyword rankings seem to transfer for the mostpart, but I haven't seen the authority or weight convey in general.
For example, domain A has the general trust and authority to to rank in the first page within 48 hours for new content. After a 301 to domain B(Note Proper 301's are important -- /subpage-content-asdf -> 301 /most-relevant-asdf) the keyword rankings convey to site B, but the authority and ability to almost immediately rank for new content does not.
2) non-www to www within a domain: From my experience, these changes are seamless if done properly. Ranking and authority seem to be fully in tact within a month or so from case studies.
3) http to https within a domain: This is the one that's surprised me. Within the past 2 years, I've had a couple sites that make sense to be exclusively ssl leadgen sites because of sensitive data gathering. I almost expected no organic success on these domains, but we previously had link campaigns and continued to the http version. What's more, we were going from [www...] -> 301 https://(no-www).
Sure enough, rankings came back to the first page for competitive terms with tens of millions of competing results indexed by google. Got to give some credit to google for this one.
I think this is a great topic that's often overlooked.
