A very long and desultory (I did it in bits with lots of unavoidable stuff in between) solve much speeded up when I read the instructions yet again and saw the bit about symmetry.
I actually didn't like this much, partly because at the end I was left with a feeling that I should have got it quicker, though Waterloo's rule of leaving it for a while definitely applied to me, and there was a lot of ice cold solving before you got anywhere, despite the early placement of the long ones.
Whereas, of course, one complains if it's too easy, this one felt like a long slog (a sentiment apparently echoed here). Good, stiff, just about fair, but it's not going to be in my shortlist for puzzle of the year.