In my previous article I wrote about how I choose my 1st pro camera. Well it was not all wild guess but the spec of the camera also has a great influence in my decision.
The only similarity of 400D with D80 and Alpha A100 is the pixel count and imaging flexibility. Other then that Canon 400D is on the other side of the river with far more advance CMOS image sensor as opposed to the CCD variants installed in the D80 and Alpha A100. And so, it is completely a different level of imaging performance and value comparison altogether.

Max resolution : 3888 x 2592
Low resolution : 2816 x 1880, 1936 x 1288
Image ratio w:h : 3:2
Effective pixels 10.1 million
Sensor photo detectors : 10.5 million
Sensor size : 22.2 x 14.8 mm
Sensor type : CMOS
Colour filter array : RGB
Sensor manufacturer : Canon
ISO rating : 100, 200, 400, 800, 1600
Zoom wide (W) : n/a
Zoom tele (T) : n/a
Auto Focus : Yes
Manual Focus : Yes
Auto focus type : Multi-BASIS TTL, 9 focus points
Macro focus range : n/a
White balance overrides : 6 positions & manual preset
Aperture range : n/a
Min shutter : 30 sec + Bulb
Max shutter : 1/4000 sec
Built-in Flash : Yes, pop-up
Flash guide no. : 12 m (39.3 ft) @ ISO 100
External flash : Yes, hot-shoe, E-TTL II
Flash modes : Auto, On, Red-eye reduction, Off
Metering : 35 area eval, center weighted, partial
Aperture priority : Yes
Shutter priority : Yes
Focal length multiplier : 1.6
Lens thread : Canon EOS EF, EF-S mount
Remote control : E3 connector, InfraRed
Self-timer : 10 sec (2 sec with mirror lock-up)
Timelapse recording : Yes, by USB cable and PC
Orientation sensor : Yes
Storage types : Compact Flash (Type I or II)
Uncompressed format : RAW
Compressed format : JPEG (EXIF 2.21)
Quality Levels : Fine,
Viewfinder : Optical (Pentamirror, 95% coverage, 0.8x magnification)
LCD : 2.5 "
LCD Pixels : 230,000
Video out : Yes
USB : Yes, 2.0
Weight (inc. batteries) : 556 g (19.6 oz)
Dimensions : 127 x 94 x 65 mm (5 x 3.7 x 2.6 in)