I paid a bit extra for faster shipping, it's now on its way so should be with me on Thursday!
I'm not sure what to expect... I've downloaded the Harmony app to my DHD - seems to work and scan WiFi for Logitech devices.
Dunno if the IR-sender thing will be much use with Sky+, probably not as it won't know what I've got recorded. Would be nice if it could search the listings, dunno if it accepts them in a standard format so it could be pointed (or proxied to) a UK feed.
I think the picture-in-picture should be fine though, it supports HDMI 1.3a which is plenty for SkyHD.
Supposedly it has a go at playing .mkvs, might be a better experience than my current PS3/mediaserver transcode method.
People are 'sideloading' apps by installing them via the browser, reports of success with mainstream ones like Facebook, Google+, Amazon Appstore, Dropbox, Pulse...