I just got the Sony a55 and the Canon T3i thanks to BHPhotoVideo.com and I’m going to do a full fledged shootout between the 2 cameras. Features, Image quality, HD Video quality and recording, High ISO Tests, ect… I’m going to be using the Sigma 30MM f/1.4 EX DC HSM on both camera bodies as it’s a killer prime lens that will yield great images and keep the testing as fair as possible.
So far my first impressions are the Sony a55 is clearly the standout with it’s incredible feature list that Pro level cameras usually only offer. 10 frames per second shooting is just one feature that comes to mind 
Also, the Translucent mirror technology of the Sony a55 makes it possible to record full HD and have the focus track automatically. Incredible to say the least with the few tests I’ve done so far.
The Canon T3i is physically much larger than the Sony a55 and it has a much better build quality/ feel to it when holding it. The Sony a55 feels more like a toy to me, kinda like the old Canon Rebel XTI. The New T3i however almost feels like a smaller Canon 60D it’s built so well. Image quality on both cameras appears excellent so far using the Sigma 30MM f/1.4 EX DC HSM Lens.
Below is a few images comparing the 2 cameras:
Sony A55 vs Canon T3i
Sony a55
Capture the decisive moment.
Change the way you shoot pictures with Sony’s new Translucent Mirror Technology™ DSLR camera. The SLT-A55V ? DSLR camera features professional-grade continuous shooting at 10 fps and visibly faster, more accurate focus in Live View and HD Movie modes. Compose your shots on either the LCD monitor or electronic viewfinder with 100% framing accuracy. Advanced features including Auto HDR, Sweep Panorama and 15-point Auto Focus make it dramatically easier to get the best shot.
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Unprecedented Image Capture
Unlike other DSLRs that can either shoot or focus with the speed and precision of Phase Detection AF, the SLT-A55V is the world’s first DSLR that can do both simultaneously1. Featuring an unprecedented Translucent Mirror, the a55V DSLR camera is able to feed both the image sensor and the Phase Detection at the same time.
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Professional Class Shooting Speeds
By transforming the fundamental way DSLR cameras work, you’ll experience best-in-class speed3, up to 10 fps continuous shooting at full 16.2MP resolution with exposure fixed at the first frame. This is made possible by a Translucent Mirror that always stays in place. You also get standard continuous shooting at up to 6 fps.
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Astonishing HD Video Capture
Experience a revolutionary breakthrough in video capture when shooting fast-moving subjects. The a55V is the world’s first camera with the precision of Phase Detection auto focus (AF) for HD Movies1. Translucent Mirror Technology not only enables full-time phase-detection AF for photos, it also delivers the same speed and precision for Full HD movies.
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Spectacular Resolution and Detail
Featuring a large 16.2-megapixel Exmor APS HD CMOS sensor, you’ll achieve beautiful image quality during both still-photo and movie shooting. Rich tonal gradation and highlight/shadow detail are assured by the BIONZ image processing engine which supports high-speed continuous shooting, advanced digital compositing, and Full HD movie recording.
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Advanced Still Shooting Features
Expand your creativity with advanced imaging features including built-in Auto HDR, which captures more scene contrast by combining the best highlight detail from one shot and the best shadow detail into one unbelievable shot. Map your journey via an integrated GPS receiver, or use 3D Sweep Panorama Mode to automatically capture expansive landscapes.
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Versatile Shooting Options
Use both the LCD monitor and Electronic Viewfinder to compose your shots. An all-electronic design enables a wide range of shooting information to be displayed in the finder and on the LCD monitor. Both provide a what-you-see-is-what-you-get preview of white balance, focus, depth of field, exposure and 100% framing accuracy, plus on-screen displays.
great