I've been listening to some recorded broadcasts of Norrington's M1 and M2 from a couple years ago (I don't have the exact dates in front of me).
Besides a couple of flubbed notes in the brass, the M1 comes off rather well, and has alot of spirit. The fanfares in the introduction were a highlight, as you could hear the difference between the trumpets onstage and offstage. I'm a big fan of Blumine, and it works well in Norrington's version, as he treats it like an intermezzo. I will problably buy the studio release at some point.
I really don't mind the no-vibrato strings, especially in the M2, where the no-vibrato sound brings a kind of starkness in the stings, giving the impression of 'painful' nostalgia, in a sense. In the Andante, the pace is a little fast, but once I got used to it I liked how this brought the music more down to earth. The first movement is down to earth too, driven with a no nonsense attitude, with breathtaking climaxes that seem to arise out of nowhere, but really effective and a nice contrast to the driven pace heard throughout. The finale is a nice surprise here. In contrast to the other movements, which sound more 'earth bound', the finale is otherwordly to the extreme (tempos are more flexible too)...the instrumental color (especially the brass) and the percussion are fantastic. The percussion crescendo is one of the most violent and loud passages in the Symphony...it seems to take forever! The soprano is good in the 4th movement, not overly operatic at all, which I like. Sorry, I don't have the timings with me at work here.
All in all, I really like Norrington's Mahler so far. The sound may be too lean for my taste at times, but at least the performance is different and interesting.
I haven't heard his M4 or M5 yet, but plan too!!