Thank you all for your comments and feedback!
For the price, the 1.8 sure is tempting!
Does the 1.8 do well in low light?
Has anyone tried one of these primes on something like the Canon XT? Buying an XT and a 1.8 seems like a relatively low cost option that would also avoid swapping lenses.
Yes, being f/1.8 means ultra good low-light performance.
The Canon equavalent is not as well built (plastic mount among others) but you would of course have the convienience of not having to swap lenses, and you'd have AF.
But, I don't think it's a good idea to start buying different brands - it could be quite costly quite quickly!
I have tried the 50mm 1.8 on an XTi (not XT) and it's really much more fun than a zoom.. And way sharper as well..
You'll be much better at composing alternative shots and such.. My advice? Go for it.. I don't think MF on the D40 would be that bad - the D40 tells you when your image is in focus anyways!