IMO, $900 is a fair chunk of change to spend. I would say unless you're going to focus on wide angle shots you might be best putting the money towards a top quality lens you'll use every day. In terms of expensive, welcome to Nikon. Canon's edge definitely shines through here
What type of shooting do you plan on doing most? What %
What next and what %
What specialty do you want to target next? How often per month?
Here's a good review of the lens you're asking about:
http://www.slrgear.com/reviews/showproduct.php/product/1262/cat/13
Another:
http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/443-nikkor_1024_3545