Body & Design
The 600D represents an evolution of Canon's long-running entry-level design, with the articulated screen being the most significant difference to a basic layout that dates back to the Rebel XSi /EOS 450D. There's a new grip for your left hand, and the mode dial reverts to a knurled (as opposed to ridged) design, but on the face of it little else is different relative to the 550D. So the body is covered with direct access buttons for most of the major shooting functions, which are used in concert with the 4-way controller or main control dial on the top plate to modify settings.
Perhaps the most important changes, though, from the photographer's point of view, are those which aren't at all obvious from simply looking at pictures of the camera. The grip is improved, and the buttons for key shooting controls such as ISO and exposure lock have been enlarged and given deeper travel, making them much more positive in use. This makes the 600D feel more like a serious tool than any of its predecessors.
In your hand
In the past we've not been big fans of Canon's entry-level models in terms of handling; since the EOS 350D they've been afflicted by a tiny, slim grips that seem to have been designed for the smallest of hands. The 600D finally addresses this with a grip that's slightly deeper, front to back, than its predecessor's, coupled with a sculpted channel on the back that provides a positive anchor point for your thumb.
This makes a big difference to the feel of the camera in your hand, and while users with large mitts may well still find it cramped, it's likely that a lot of users will find the 600D much more comfortable to hold than its predecessors. Overall it's the first entry-level Canon that we've been happy to carry around one-handed for an extended session of shooting since the original 300D.
The EOS 600D appears to use a very similar pentamirror viewfinder to that in the 550D; the specifications indicate a marginally decreased magnification (0.85x vs 0.87x), but this is too small a difference to be noticeable in practice. That aside it's identical in terms of markings and information displayed - see our EOS 550D review for more details on this. Again this means (as we said then) that it's one of the better pentamirror finders out there, but obviously is not as big or bright as the pentaprism finders generally found in more expensive cameras.
Canon was one of the very first manufacturers to use an articulated screen on a digital camera, dating right back to the Powershot Pro70 of 1998. For a long time the company seemed curiously reluctant to use one an SLR, but after 12 years of waiting, now two have turned up in quick succession. The 600D uses the same excellent 3:2, 1,040k dot display as the EOS 60D, with a side-hinged design that allows unobstructed movement even when using the camera on a tripod (something that tends to be a disadvantage of base-hinged designs).
Swivel-and-tilt screens have undoubted benefits. They're great for shooting at awkward angles, perhaps on a tripod or with the camera held above your head, and provide a much more stable platform for shooting movies. We noted though that the usefulness of the 60D's screen is compromised by its distinctly hesitant live view contrast-detect AF, and the 600D unfortunately hasn't improved in this regard (it does share the same sensor and processor after all).
There is a workaround, which is to use the 'Quick Mode' AF in Live view. This flips the mirror down and uses the conventional phase detect AF system (as used for eye-level shooting) instead, then brings the mirror up to resume live view. This is much quicker, but it does result in the momentary loss of live view which is accompanied mirror operation noises. Because of this we found it works best if you assign AF to the '*' button on the back of the camera (by setting C.Fn IV-9 to 1: AE lock/AF) as otherwise you'll lose live view every time you half-press the shutter.