If you want to sum up Steve Hillage's musical career in a single boxed set... well, actually, this wouldn't do it, but it comes incredibly close.
As well as containing all of his original run of solo albums (including Live Herald) and a brace of live sets (including full versions of the 1976 and 1979 BBC sessions, tracks from which which had previously been released in an abbreviated set, and the previously released Deeply Vale set and 2006 Gong Unconvention set, as well as several never-before-released gigs), you also get a stack of demo material, the original albums from Arzachel and Khan on which Steve cut his teeth, and you even get the first System 7 album to give you a little taste of where Steve and Miquette Giraudy (his partner in life and music since the early 1970s) are directing most of their creative energies these days.
The major gap, then, would be his Gong-era work, though to be honest you'd really need a whole separate boxed set to contain all that and the rights issues there are likely to be a bit of a landmine.
As far as the previously unreleased live sets go, BBC Radio 1 In Concert 1976 offers a strong, punchy run-through of best material from Fish Rising and L, which sells me on the idea of Hillage having a really forceful backing band better than L did, whilst the 1979 BBC material has Steve and the band delivering an unexpectedly funky attempt at the material, almost as though Steve were testing out a left turn into Young Americans-type territory.
Live at Brighton Dome showcases how on the Motivation Radio tour Hillage wove his shorter songs from that album and extracts from the longer works which were highlights of Fish Rising and L into wild journeys, or unfolded individual songs into long extended jams, and is probably the best of the live sets here. Live at Schwaubinger Bräu, Munich and Live at the Odeon Hammersmith are both OK sets marred by shaky sound quality, though not as bad as the horrible sound quality on Deeply Vale.
In all honesty, this is probably more Hillage than anyone actually needs - out of the stuff on here which you couldn't otherwise get elsewhere, I'd probably only want to hold onto the 1976 BBC set and the Brighton Dome gig. But if you really want to wallow deep in Hillage's discography, this is as close to a definitive career retrospective as you're ever likely to find.