my sis in law has a new D90. though i like the cam due to its high resolution lcd, hand grip is better than my unit, can AF old lenses, but i find it not worthy of an upgrade to the D5000. i do take note that these 2 Nikon DSLRs belong to the same class, the Mid-Range Level. (dont argue that D90 is a semi pro) if ever i will upgrade, it would be higher than the class of these 2; maybe D300, 300S or Canon 50D, 7D.
i also take note that D90 has the same sensor, pixel, and almost (frames per second) with my D5000. the big and noticeable difference is the price gap
Plus a host of other features like CLS, 2 dials, top LCD which may not be what everyone need.