why do you want d90 over d3100? or do you just know what you are buying?

ofc, I'd go for d90 for sure If I had the money. d3100 It's my second choise depending of my cash

why is it your second choice? d3100 is better than d90 in some aspects

LOL
ONLY if you are worried about video
the rest D90 > D3100

ye

yeah video is better ... but still.. theres not THAT huge a different on the 2 overall.. considering d90 with lens is almost twice the price

I don't think you can use older Nikon lenses and those without AF motors with the D3100 other than that the D90 also offers much better ergonomics and offers faster burst speed.

http://www.digitalphotographywriter.com/2010/11/nikon-d90-vs-d3100-vs-d7000-free.html

just for the af i would get d90 over d3100. also the 18-55 kit lens is in most people top 10 nikon lens's of all time. its so sharp. i own mostly top end pro lens but the 18-55 is still as sharp as any of them. the only drawback is the f3.5 aperture and its made out of plastic. but if it breaks buy another one they are so cheap. Any one that says otherwise has never owned/ used one

Well I don't know much about Nikon lenses but you do know that sharpness is not everything especially center sharpness. I know some of those plastic kit lenses and other low end lenses are sharp in the center but their corner sharpness are pretty awful. Also when it comes to lenses you have to look at other characteristics too like bokeh, contrast, af speed etc. Though not everyone is willing to pay the extra for high quality lenses and for many the cheap kit lenses are all what they need.

d3100 has better ISO handling, higher max ISO and overall better IQ, but the difference with overall IQ isnt all that big.