I finally got the set and love it, especially the new extended mixes! Just to add more info to the list of mixes TJL posted:
The Miracles - Mickey's Monkey has an extended mix on the original Motown Box, but the new one is extended even further [[50 seconds longer with a cold ending!)
Martha & The Vandellas - Heatwave is the same length as the original Motown Box, but this one is mixed better than the old one. [[There's also a third extended mix on their Gold CD.)
Four Tops - It's The Same Old Song has an extended mix on the original Motown Box [[which goes on longer than the new one) but the new one is an alternate mix.
Four Tops - 7-Rooms Of Gloom is an extended stereo mix of the alternate mix that first appeared on their Fourever box set in mono. The new mix also has an extended instrumental intro.
The Marvelettes - The Hunter Gets Captured By The Game has an extended instrumental intro and unfaded ending, but sadly doesn't include the extra verse.
I also tried to figure out which extended mixes from the original Motown Box made it to this set and here's the ones I found:
Mary Wells - My Guy [[extended stereo mix)
Four Tops - Baby I Need Your Loving [[extended stereo mix) [[it only has an extra "Baby I need your loving, got to have all your loving" at the end, so it's not really that extended.)
The Temptations - My Girl [[extended stereo mix)
Jr. Walker & The All Stars - Shotgun [[extended stereo mix)
The Miracles - The Tracks Of My Tears [[extended stereo mix)
Stevie Wonder - Uptight [[Everything's Alright)[[extended stereo mix)
The Miracles - Going To A Go-Go [[extended stereo mix)
Jimmy Ruffin - What Becomes Of The Broken Hearted [[alternate spoken-word beginning, extended stereo mix)
Marvin Gaye & Tammi Terrell - Ain't No Mountain High Enough [[extended stereo mix)