And what is the point of having to download and extract logs from a zip file? That's not good UX. My friends and I are completely baffled that this MOST basic feature doesn't work as expect.
Here is how it should work: I log in at home and I get full history of the channel (or as much as they keep, but at least last 24 hours), so I can see what's been going on. Then I leave for work (I leave my client open at home) and during commute I might popin and see what is going on, again I should get full history regardless what has happened while I was gone (or if nothing had happened). Then I get to work and again I should get full history of all messages and all these clients should get updated history whenever there are new messages.