Not much larger than a bridge camera, starter digital SLRs are inevitably more compact than their body toughened, weather-proofed semi pro big brothers and the D3100 is no exception. However the build feels solid - lightweight yet robust with it, particularly with the 18-55mm lens attached, and not obviously plastic-y.
One area that suffers in the need for the DSLR to appear unthreateningly compact to newcomers is the hand grip however, being smaller and less comfortable than we would have liked. You can curl three fingers around it, but it's a squeeze. This leaves the forefinger hovering over the shutter release button, located on the forward slope of the grip, and the thumb resting on a small rubberised pad at the back, or more likely the command dial just above. There's no time saving front command dial though, as on higher-end DSLRs, nor is there a top-mounted LCD window for a quick glance at key settings.
The D3100's chunky shooting mode dial, the width of a 10 pence piece, sits in its usual place, slightly backward slanted for more comfortable access via forefinger and thumb, slotting into each setting when turned with a definite 'click'. So you're unlikely to jog settings accidentally when lifting the D3100 out of your camera bag. The dial has the usual smattering of auto settings and enhanced subject specific options that will enable the less experienced to point and shoot to begin with and move on to experimenting with the creative quartet of program, aperture priority, shutter priority and manual as confidence and natural curiosity grows.
A stiff lever to the right of this provides access to the camera's various drive modes, ranging through single shot, continuous burst, self-timer and, usefully for those attempting candid portraiture (whether humans or skittish wildlife), a 'quiet shutter' option. Although there is some mechanical sound with this last option selected, the camera 'kills' the beeping noise that usually signals focus and exposure have been determined - so your subject isn't alerted to the fact that you're about to fire off a shot before you do. We still get auto focus points flashing red in the viewfinder as a visual signal.
The shooting information displayed on the backplate LCD upon start up doesn't automatically switch off as an eye is brought to the viewfinder, which would have been nice to avoid its slightly distracting glare, as the D3100 doesn't feature nifty built-in eye sensors like the Sony Alpha series. It goes off of its own accord eventually but then 'pops' back into life as you half press the shutter release button having lined up a shot.
Like previous DSLR generations the look of the display is changeable - from 'classic' to 'graphic' and vice versa, whilst background colour can also be swapped to suit personal taste and aid legibility.
In general terms the Nikon's buttons and controls are well labelled, practically sized and effectively implemented, plus fall under thumb or finger without any awkward dextrous feats required.