Had the same choice a couple of months back and went for the 35mm.
Must admit, I was tempted for the 40, but the extra hundred quid (at the time, might have changed now), couldn't be justified as I had just been given a nice electric bill

- I also had a 50mm 1.8d and felt 50 was too long for indoor lowlight (where I will use these lenses most).....
Glad I got the 35 now - really cant see how you can get much 'sharper' to be honest. (I use a D3000)
There was some talk of purple fringing and a few other 'distortions' - I've seen none, and to be honest unless you are working in Nikon lab, I doubt anyone would think of it as anything less than 'sharp'. Great walkabout.
With the 40, I dont think you will get 2.8 on macro either - but from what I understand thats pretty typical - from what I remember it will got to 4 or something around there.
For my indoor dim light shots, there is a big difference between 1.8 and 2.8 as well

Tempted for a macro lens, but not 40mm - I'll get something upward of 80/90 - a decent starting length for macro, but also ideal for my portrait stuff

Get the 35 and a 'proper' macro

Dont think you'll be catching the wrinkles on a spiders brow at 40mm...could be wrong though - just saying the 40 seems to be a gap filler from Nikkon (jack of all trades type of thing...) There's no way of getting round the fact one lens wont do it all:shake:.