d5000 user here, bought it due to its value for money at a recent comex. love many features such as the swivel screen.
But for those deciding between the d90 and d5000: the d90 has more knobs and buttons which make changing of aperture, shutter speed, exposure and iso much faster in manual mode. for the D5000 you are limited to only 3 variables. however i am quite okay with the trade off because of its price.
my BIGGEST problem is its inability to trigger off board flashes by infrared i.e. the on-board flash HAS to fire before any other flashes can by fired. so in order to overcome this,i'll have to spend extra to get a su800 or a sb900 to trigger an external flashes. a d90 user would be able to settle for a sb600 if his budget is tight.
also the lack of an inbuilt motor limits the lenses available to me. of course i can always focus manually, but i would take that into consideration when looking at the cost of a lens.
so in the end, does the price of the d90 and d5000 balance out? if you decided to stop at just the camera and kit lens, the d5000 would be the best investment. otherwise, a d90 would be better than in the long term IMO.
PS i get the feeling the canon equipment is cheaper=(