I've been a pro photographer for very many years (over 40) and very much love digital cameras which perform far better than the old 35mm film cameras. I've owned a few Nikon digital cameras; D50, D80, D300S, D5100 and currently a D3100. I've used generally a 35mm prime, 18-200 VR and currently a 16-85VR and have not used the bundled kit lens that comes with the 3100. Now obviously the 300S is a better specified camera than the 3100 and more expensive, but in all honesty one does not find oneself using all the extra facilities provided on the more expensive camera- they really aren't necessary and when you look back at the earlier film days we had none of this proliferation of controls. So in many ways using a 3100 is not a lot different from a 300S- all things being equal.

*The rear screen doesn't quite have the resolution that other Nikons have, but this is no real big deal and I never use the so called live view.
*The viewfinder does not have such a large view area as better Nikons- again this is no big deal as long as it is sufficient to frame up your shot.
*Exposure is occasionally 'over', but this is no different from other Nikons I've used.
*Yes the battery and memory compartments are leaning slightly towards the flimsy but you should be careful with cameras anyway and not subject them to the sort of rough use that could damage these areas.
*The row of buttons along the left hand edge appear to be mounted as one strip of controls under the back panel instead of being individually mounted- something I'd not noticed on previous Nikons.
*Personally I don't find it a problem to have to use the nested menu system to change settings as opposed to having dedicated buttons on the outside of the camera- I'm not in that much of a hurry...
* I don't really know how weather proof the 300S was or if indeed it was any more weather proof than a 3100, so I'm never too keen to get these type of cameras too wet in the rain.
*I'm using the same lens on the 3100 as I did on the 300S and it appears that my images are as good and as sharp which indeed they should be.