Hi Stu,
I was wondering about these as well after first reading about them on the Steve Hoffman Forum. But just now, after checking the track list on amazon.uk, I'm happy with my Repertoire editions. Unless they've been remastered with better sound (and like you, I think the Repertoire's have amazing mastering), there's nothing more to be found here. And we actually have two extra tracks on Faintly Blowing then are available on the new Grapefruit set.
I'll ask the question at STF and see what the consensus is...

I've just got the new Grapefruit release, and I'd say the sound is a little bit sharper than the Repertoire releases - and of course, it's nice to have all their tracks under one roof. And like the other Grapefruit releases I've got, the booklet is beautiful, with rare photos and very good liners.

I guess whether you need it if you've already got the Repertoire ones depends on your point of view, but I'm glad I got it.

I've only got the vinyl reissue on 5 Hours Back from a number of years ago.
So the Repertoire comps actually have more tracks than the Grapefruit one Mark?

Yes, at least according to the track list at amazon.uk. Tangerine Dream includes the same bonus tracks in the same order:
Flight From Ashiya (Mono Single Mix)
Holiday Maker (Mono Single Mix)
A Dream For Julie
Please Excuse My Face (Mono Single Mix)
Jenny Artichoke
Just How Much You Are
And Faintly Blowing is also identical, but the Repertoire also includes the "Special Bonus" tracks:
Let The World Wash In and Mediaeval Masquerade, the A&B-Side of the 1970 Philips single 'I Luv Wight'.

Both came in digipak with 12 page booklets... lots of photos and memorabilia. Faintly Blowing has the inner gatefold with lyrics (but you need a magnifying glass to read them of course). Liners for TD were written by Chris Welch and FB by Nigel Lees.