Overall handling and operation
The 600D is essentially the same as the 550D in terms of control layout, which isn't a bad thing at all. The Rebel series' control layout has developed in an evolutionary manner, so presents very few surprises. It's not got a super-simplified first-time-user style interface of the style that's becoming popular in really low-end DSLRs and mirrorless cameras, but it's still clear and simple to use. It's a camera that will be straightforward for most people to use, and easy to get the most out of if you have any experience of DSLRs or enthusiast compacts.
Specific handling issues
In general, there's not a lot wrong with the 600D in practical use. Most of the key controls are well-placed, and the camera handles well for conventional eye-level shooting, although AF point selection is a little less straightforward than on cameras which use the 4-way controller directly. Also the exposure compensation button is perhaps a bit too close to the viewfinder for really comfortable use, especially if you wear glasses, but it's not troublingly bad.
Our only significant criticism, beyond these minor handling niggles, is the inconsistency of behavior between conventional shooting and live view / movie mode. Despite the cardinal points of the four-way controller being marked with specific functions, they are all given over to AF point positioning as soon as you engage live view, with their usual functions accessed via the Q button. We regularly found this inconsistency disconcerting; it's all too easy to find yourself inadvertently moving the AF point around when you really wanted to change drive mode, for example. This isn't disastrous but it can be unhelpful, particularly for people trying to learn the camera.
Not surprisingly a number of Canon's long-running interface flaws are still in evidence, too. Mirror lock-up is inconveniently buried in the custom function menu, and when enabled allows no quick method of switching back to normal shutter button behaviour. Why Canon can't simply implement it as a separate drive mode, perhaps as a mirror pre-fire when using the self timer like several competitors, remains a mystery.
The annoyingly long-winded method of setting a custom white balance remains too. The 600D requires you to take a shot of a white or grey card, designate it as a reference image, and then manually switch to the custom white balance setting (as the camera seems unable to comprehend that having selected the reference image, you probably want to use it). The more standard method of pointing the camera at the reference target and using it directly to set a Custom WB frankly makes much more sense.
The useful Highlight Tone Priority mode can be configured separately for stills and movie mode, but rather oddly appears in entirely different menu locations for each. In movie mode, it's a top-level item in the Shooting menu (which is exactly where it should be), but for stills it's hidden away in the custom functions. We find it hard to make sense of this - when the comparatively trivial 'Bass Boost' option that only affects in-camera video playback is made a top-level option, why is the same status not accorded to a feature that can profoundly affect the quality of your images?
The 600D is reassuringly fast camera - it's unusual to find yourself waiting for it to react. Pressing the menu, Q.Menu or playback button results in a near-instant response and the behavior is similarly swift when shooting. Only in the transitions to and from live view is there really any lag during which the camera is inactive. In most situations the camera is fast enough that you don't notice it - which is the key measure of it being fast enough.
Continuous Shooting and Buffering
The continuous shooting rate of the 600D is one of the biggest distinctions between it and the more expensive 60D (along with its smaller viewfinder and single dial control, etc). It attains a respectable, though not exactly blistering 3.6 fps in all its image modes, but can maintain this for just three frames in raw + jpeg mode, and 6 frames in raw only. Because it takes 8 seconds to fully clear its buffer in these modes, it's not terribly useful for shooting short bursts of action, since there's every chance the camera won't have recovered by the time you need another handful of shots. If you find yourself trying to shoot sports or action, you may find yourself better-off taking a metering and WB test shot then shooting JPEG, which gives a much more respectable 40 frame buffer.
- JPEG: 3.6 fps for around 40 frames, then around 2.7 fps. 4.5 seconds to recover.
- RAW: 3.6 fps for 6 frames, then around 0.77 fps. 8 seconds to recover.
- RAW+JPEG 3.6 fps for 3 frames, then two slower frames followed by 0.5 fps. 8.5 seconds to recover.
All tests conducted with SanDisk Extreme Pro 45MB/s SDHC UHS-I card.
Autofocus speed / accuracy
In-line with the 'slightly revised 550D' theme of this camera, its AF system is essentially the same as the older model. This means it offers an eminently respectable 11-point AF system that performs quickly and reliably. It's not nearly as sophisticated as the AF systems in Canon's more expensive cameras, so don't expect it to track and shoot to the degree required for pro-sports shooting, but it's as easy to use and dependable as you could hope for of a camera at this level.
In live view 'Live Mode' the whole package is considerably less impressive - the accuracy is fine but focusing will regularly take 3-4 seconds. This not only rules out its use for moving subjects but, in doing so, also significantly undermines the usefulness of the articulated screen for hand-held stills shooting. Of course this also means that the 600D isn't very good at refocusing if your subject moves while you're recording a movie.
It's disappointing to see that Canon has made essentially no progress on this front, while other manufacturers have improved their SLR's live view AF considerably. Ultimately it means that the 600D's usability in Live View and for movie shooting is some way behind most of its competitors in this regard.