The following section is organized by the variety of photographic scenarios LANDSCAPE, MACRO, NIGHT, PORTRAIT and SPORTS photography.

Nature Photography

At around 600g the Sony A550 is the biggest and heaviest camera in this group of three consumer cameras consisting of the Canon EOS 500D and the Nikon D5000. However, therefore you can save the weight for a spare battery due to the great battery life of approximately 950 shots.
Unfortunately, these days more and more cameras are offered without a DOF-button and that's also true for the Sony A550. This is bad news for people who want to preview the depth-of-field but this would be difficult with a smallish APS-C class viewfinder anyway.
As already mentioned during the body tour the quality of the small viewfinder is only about average at best. The AF sensor indicators fade out after focusing and there no super-imposable grid lines. As odd as it may appear but without guiding lines or marks live view seems to be a better alternative for image compositions at times.
The most annoying think in respect to outdoor activities is the bad dust reduction system of the A550 and I recommend to carry an external solution with you on outdoor missions.
When talking about available lenses for great landscape shots the Zeiss ZA 16-80mm f/3.5-4.5 DT is an obvious choice. The Sony 11-18mm f/4.5-5.6 isn't all that great though so you might have a look at third-party options here. The Sony 70-300mm G or Sony 70-400mm G are obvious choices with respect to wildlife photography and for the professionals there's the Sony 300mm f/2.8 SSM G.

Macro Photography

Macro photography means Live-View these days and, just like all the competitors, Sony offers this feature in combination with the great 3"-Xtra Fine-LCD with a resolution of almost 922k dots and their outstanding Quick AF which is pretty fast due to the conventional AF during live view. Furthermore, the A550 comes with a tiltable display for more creative macro shots but unfortunately only in vertical direction - this is pretty useless in case of vertical shots. Further useful equipment like Ring-/Twin-flash and wired remotes are available. The number of macro lenses is very small in Sony land, however the with a very high resolution potential or the Sony 100mm f/2.8 macro, which is able to produce very sharp results combined with a negligible amount of distortions, vignetting and lateral CAs, are good lenses to start with.

Night/Low-Light Photography

The Sony A550 is reasonably suitable for night/low-light photography. Its high ISO performance is rather typical for an APS-C DSLR and as such not overly impressive beyond ISO 800. The long exposure noise reduction works fine so tripod-based night images are no problem. As usual bulb exposure is available but it's not programmable so the the exposure button has to remain pressed during the whole exposure.
The viewfinder is quite small and dark and so it's not easy to compose your scene in dark conditions. Furthermore, Live-View is no better alternative here as there is no sort of "low-light amplifier" available and the image is as dark as the view through the viewfinder.
Finally, Sony follows with SteadyShot the trend of camera build-in image stabilizers. This sensor-shift mechanism is comparable with Canon and Nikon lenses with built-in image stabilizers and offers - according to the Sony website - compensation of up to 4EV steps. However, this varies according to shooting conditions and lens used.
Good high speed prime lenses with Sony/Minolta mount are quite rare at this stage except the Zeiss ZA Planar T* 85mm f/1.4, which is already able to produce exceptionally sharp and contrasty results straight from f/1.4.

Portrait Photography

Generally, the A550 provides all camera features required for portrait photography as well as a face recognition system including a smile detection system that can be switched on. A cute gimmick but not really needed for more serious portrait photography.
More important is the selection of special portrait lenses with a typical focal length between ~50-135mm and the already mentioned Zeiss ZA Planar T* 85mm f/1.4, with a beautiful bokeh (out-of-focus blur) might be a good alternative.
However, at around 1200EUR/US$ the Zeiss ZA 85mm f/1.4 isn't cheap but definitely worth a deep thought regarding its optical qualities and the selection of Sony lenses in this segment is actually very modest.
Last but not least, the min. X-sync of 1/160sec is generally fine for portrait photography and furthermore high-speed sync. is also available with external flash units.

Sports Photography

At up to seven frames per second in speed-priority continuous mode (The exposure and focus are set at the first shot) the Sony is more than geared for fast sport action shots. In RAW mode however, the frame rate slows down after 32 Fine JPEGs or 14 RAW images in succession due to the memory buffer. Nevertheless, the AF speed and the accuracy of the Sony A550 guarantee sharp sports pictures even in continuous AF mode. The maximum shutter speed is 1/4000s – nothing special here but usually sufficient for most kind of action photography.
Sony's lens portfolio shows some interesting but unfortunately expensive tele lenses, like the very good Sony 70-200mm f/2.8 SSM G, which certainly deserves its "Gold" class designation or the "cheaper" Sony 70-300mm f/4.5-5.6 SSM G with very good resolution figures across the zoom range.