I'm a huge Gentle Giant fan and Steven Wilson's mixes, and I usually agree with the average QQ ratings of surround releases. I had been very familiar with GG's original mixes prior to the remixes. In my opinion Steven dropped the ball in his approach to this band, and The Power and the Glory is the biggest victim. This is not so much a remix, but rather re-make which mostly misses the original spirit of the recording.
Gentle Giant is a very fitting name for the band. Light on the bottom end and a very open, airy, large-soundstage type of music. Steven made the bottom end much more pronounced, thus overpowering the mids and highs. I appreciate that the original mix of The Power and the Glory was way too bright, but the volume of the rhythm section in the remix is just insane, flipping the problem on its head. The end result is a very aggressive sounding album without the spaciousness of the original. The name of the band could have as well been 'remixed' to Angry Midget on this release.
Listening to the 5.1 is a rollercoaster of changing the volume to keep up with having some enjoyment of the songs while avoiding the obtrusive outbursts of the drums. Overall, I find the experience more unenjoyable than enjoyable, therefore a 5 from me. All the typical characteristics of a Steven Wilson 5.1 mix are there, so if you're not bothered by how pronounced the rhythm section is on this one, I can see it being a 9 or 10 for you.
For reference, this is how I rate the rest of the 5.1 GG releases:
1. Gentle Giant/Unburied Treasure - 10 (the only album unscathed by the above issues)
2. Three Piece Suite - 9
3. Free Hand - 7 (I'd give the channel layout-corrected quad mix a 9)
4. Octopus - 7