the Canon EOS 5D's build quality is excellent. The rugged body is composed of a magnesium alloy and stainless steel chassis (including the optional BG-E4 Battery Grip). Although this is not a dust and weather sealed design, the feel is solid and sure. Next to the 1-Series bodies, this is my favorite Canon grip thus far. A sculpted Canon logo, electroplated "EOS 5D" badge and higher density matte finish complete the quality look and feel. The 5D is one of the quietest Canon DSLRs currently available. Listen to the 5D's shutter sound and frame rate compared to the Canon 20D ... 5D 3 fps Burst 20D 5 fps Burst The Canon EOS 5D is equipped with a newly developed 9-point AF unit with 6 invisible Supplemental AF points. Results include improved AI Servo AF subject tracking and improved focusing from a defocused state. I find the 5D's autofocus to be both fast and accurate - even in low light situations. Although not quite as good as the 1D Mark II and 1Ds Mark II, the 5D performs well for real AF challenges such as action sports photography. My AI Servo AF hit rate through several soccer games was slightly less than what I generally see with the 1Ds Mark II, but still very good. The 9 AF points span approximately the same subject area as Canon's other Digital SLRs. Like the 20D, the 5D requires a lens with a maximum aperture opening of at least f/5.6 for AF to function. Canon's 1-Series bodies can AF with a maximum aperture of at least f/8 (1-stop less). All modern lenses have 5D AF-compatible apertures - the difference comes when adding extenders to these lenses. To learn more about the 5D's AF technology, read the white paper (link below). The Canon EOS 5D's Image quality is excellent. This should be a surprise to none. As a broad statement, I would say that the 5D's image quality falls between the 20D and the Canon EOS 1DS Mark II - more because of the number of pixels than anything else. Dynamic range is good, but appears to be slightly closer to the 20D than the 1Ds Mark II. The 5D expands the 20D's ISO 100 to 1600 to include ISO 50 and 3200. In addition, the 5D allows 1/3 increment stops. Noise performance is similar to the 1-Series Mark II bodies and very slightly better than the 20D. he 5D's features and functions are extensive - there are very few pro or prosumer functions not included. I will leave the complete list to the retailers and Canon's white paper (linked below), but will touch on a few additional ones - especially differences between the 5D and the 20D. The 5D has far fewer shooting modes than the 20D. With the exception of the Full Auto (point and shoot) mode, all of the basic modes (Portrait, Landscape ...) have been removed. Most people moving to a camera as advanced as the 5D do not use these modes anyway. New on the mode dial is a new 'C' (Camera User Setting) selection. Setup the 5D for a certain situation and save the settings (including custom functions - which include mirror lockup) to 'C'. When you want to immediately recall these settings, simply turn the mode dial to 'C'. Be wary of powering down the camera - or having it go into sleep mode - while in 'C' Mode. The camera likely will revert to the stored 'C' Mode settings even if you have altered them prior to power down/sleeping. The 5D has 3 interchangeable focusing screens available. Most users will stay with the standard focusing screen, but this option will be important to some. The 5D adds user selectable folders. This is a nice option for those who want to organize their shots into specific folders. Create a new folder, select it and begin shooting. Do the same again for the next set of shots you wish to keep grouped together. New image viewing jump options are available on the 5D. You can jump by 10 or 100 images, by date or by folder. This makes finding a specific shot easier. The 5D's full-frame sensor is certainly one of it's biggest selling points. Photographers have been asking for an affordable full-frame Digital SLR since DSLRs were first produced. Landscape and other wide angle photography needs are better met by a full-frame body. Portrait photographers want the shallow depth of field attainable with the larger sensor. The 5D is Canon's answer to these needs. Although it will be a long time before the goal is realized, Canon plans for all but the least expensive DSLRs to have full-frame sensors in the future. Like the 20D, the 5D is powered by a Canon BP-511A Battery Pack. With a fully charged BP-511A (or BP-514), Canon indicates battery life at approximately 800 shots at 68°F (20°C) or 400 shots at 32°F (0°C). My first fully charged battery delivered 743 shots in my normal use, my second delivered about 800 shots. This includes a 4 second shot review, a fair amount of image reviewing and a lot of powered-on-but-idle time over 2+ weeks. I have a heard a fair amount of complaining about the "poor" battery life of the 5D. What may not be understood is that there can be many shots left when the battery low indicator shows. Those without a spare battery or those who can't have the battery die at an uncertain moment use this indicator to recharge/replace the battery. The low battery indicator first showed after about 400 shots, the low battery indicator began flashing at around 600 shots. The battery went on working for another 143 shots for a respectable 743 total shots. That is a lot of pictures from a small, light battery. The optional battery grip allows two batteries to be used simultaneously for approximately double the number of shots from the 5D. Power performance from the Canon EOS 5D is excellent. Power-on seems instant and all features and functions are responsive. Playback performance is very good as well. The 20D and 5D also share the same CB-5L battery charger. I appreciate the compact design of this 90 minute charger. The 5D will appeal to both advanced amateurs and professionals who need or want very high image quality, wide angle field of view and/or shallow depth of field but do not require a high continuous frame rate, durability or weather and dust sealing. Those needing higher frame rates (typically sports and sometimes wildlife photographers) should consider the Canon EOS 20D or the Canon EOS 1D Mark II N as alternatives. Those wanting the ultimate image quality should consider the Canon EOS 1DS Mark II - an incredible camera The Canon EOS 5D represents a great value in a high quality, high performance, full-frame Digital SLR. You get excellent quality, high resolution images for less money than ever before. I found very little to critique or complain about. This camera will exceed the requirements of many photographers. Its pretty good.......