If we are comparing Haitink to himself, I still prefer his original with the Concertgebouworkest over this new one. I don't dislike this or think it's bad at all, but this is not my style of M7. You're right, it's just a bit too lethargic for me. Although it is very 'maturely' conducted (I don't even know what I mean by that but somehow it makes sense to me).
I like what Haitink does with the third and fourth movements – a lot.
The percussion does plenty of good work here, especially the timpanist. I would've liked to hear what they could do in a faster finale (especially after the screw-up old Jansons recording where they got a few bars ahead in the middle).
I like the first movement, but again not as much as my favorites. I think the middle ("moonlit") section works very well here.
I really, really want to hear Harding's take on M7 now, especially if the orchestra is sounding this good in M7 these days. I guess I'm just not a big fan of Haitink's late Mahler.