I've been listening to quite a bit of SM over the past few weeks and here's my current read.
First, the original run of albums, at least the early ones, is really great. Albums 2-4 in particular are wonderful to listen to.
Second, the archival releases I have (Noisette, Virtually) show that as a live unit, they weren't in the same tier as the top American jazz-rock contemporaries that were mining similar terrain (esp Weather Report and the Miles Davis bands). That's not surprising because the caliber of improvisers/visionaries was so exceptional in the elite American units, i.e. Soft Machine does pretty well if you bracket it with the next tier of Americans.
Also worth adding that they definitely brought something new and innovative to the table. There are flavors in the SM gumbo that you don't get when you listen to WR or the MD bands.