I tried a 50mm AF on my D40 but found it far to hard to manual focus it, maybe just me but I missed a lot of good photos of my son because the focus was out.
I got a AF-S 35mm f1.8 which did auto focus and got a lot more enjoyment out of that.
Of course is all about personal choice, just sharing my experience.
Not sure what model you are getting , but the 50mm 1.4 AFS is £100 more expensive than the 35mm AF-S, make the right choice the first time!!
I preferred the 35mm on the crop sensor, as for me the 50mm was too close in and I had to stand further from my son, not always possible to get same light as easy then.
i'm going to sound like a total alkie now
portraitwise;
50 mm for 6ft to 10ft across the pub
35mm for 4ft to 8ft across the pool table
28mm for when you are shooting across restaurant and bar tables.
it takes time to get comfortable with them. and manual focus with stopping down is a pain in the bum at times.
i got the canon 50 first and freaked but soon became used to it.
I then inherited the leicas and it's taken me 6 months to get comfortable with them, using the 50 f2 first and gradually forcing myself to use the ones that confused me.
Then before you know it you get hooked and now my camera bag weighs 25kg and i spend half my life changing lenses.
Seriously, using zooms can feel like a day off but some how isn't so rewarding.
the 50 us a great FL to start with because it helps you to understand the others.
ftr
i also have a 60 macro, 90, 100 macro with bellows, 135, 180, 200, 280 and a 400 but the last four still freak me out.
old lenses are so worth investigating, i feel that the leicas give me an edge in my creative and portrait photography.