No surprises in the the Alpha 550's playback mode - it acts like pretty much every other camera on the market. You can view the image with various levels of detail, you can zoom in or out and, usefully, you can jump between images while zoomed in order to compare critical detail and focus. You don't get much in the way of fancy playback features: there's no raw conversion, no special effects and no musical slideshows here, just the bare basics needed to review saved images.
No overlaid information
Overlay (quality & size, date & time, file number)
Shooting info and histograms
Pressing the magnify button zooms in on an image, rolling the control dial jumps between images.
Pressing the zoom-out (exposure comp.) button jumps you to the thumbnail index views. Pressing the Fn button toggles between the two different index views; 4 images (2x2) and 9 images (3x3) and a folder icon on the left-hand side lets you jump between folders on your memory card.
Other play functions
From the thumbnail view you can jump to another image folder on your memory card.
From the menu, you can choose to protect or delete selected images.