The P90's automatic white balance is noticeably worse than the P80's--the blue channel is really weak--and a non-neutral white balance tends to exacerbate noise visibility. Here you can see that sharpness decreases markedly at ISO 200, and even below that everything looks a bit overprocessed. Unfortunately, even at ISO 64 there's visible color noise in even slightly shadowed areas (not shown).
This example displays a lot of the different problems with the P90's photos. First, you can see the generally pervasive color noise even though it's ISO 64 and not a particularly dark shot. You can also see the smeariness from the noise reduction, fringing, haloing on edges, and generally "digital" look to the photo. (ISO 64, f3.2, 1/125 sec, 26mm equivalent, pattern metering)
The P90's lens, at its 26mm-equivalent wide angle, displays typical barrel distortion (top). Using Nikon's in-camera distortion control (bottom) fixes the curvature but not the angling of the lines; that's common for systems like these.
In sunlight, the automatic white balance works pretty well, although photos still seem to have a little too much yellow in them. Nonetheless, color look pleasing, saturated and bright, and are sufficiently close to accurate.
As long as you're not planning to print larger than 11x16 inches, the detail from long shots is acceptable, though not great. The harder part with such a long lens is getting the camera to focus on the correct subject; in a lot of these shots, the camera kept focusing on the fountain instead of the bird. There's also quite a bit of fringing on the highlights on the fountain, which become quite visible in 8x10 prints.(1/250 sec, f5, ISO 64, spot metering, 624mm equivalent)
It may have a long lens, but at heart the P90 is a point and shoot, with a lens that can't really resolve detail in shots like this. You can also see the fringing and haloing. However, the default (pattern) metering does pretty well and the exposures are generally very good. (1/60 sec, f7.1, ISO 64)
Macro shots are usually the sharpest a camera can do, and while this looks sharp when zoomed out, close up it looks processed and very digital. The color of this flower is also a bit shifted; it should be redder. (1/60 sec, f4.5, pattern metering, auto white balance, ISO 64)