At least externally there's not much to distinguish the EOS 500D from its predecessor the 450D. The body is identical, a conventionally-styled SLR shape with a comfortable handgrip. The body is made of a strong but lightweight polycarbonate plastic and the build quality is excellent, with no gaps at the body seams. The control layout is also identical to the 450D, with the additional functions added to existing controls.
Although the camera doesn't claim any weatherproof credentials the body and hatches are well protected against dust, and the card slot hatch has a strong metal hinge. I commented in my review of the 450D that the body felt flimsy. This is not something I would say about the 500D, although that may be because I've seen more entry-level cameras recently rather than any change in build quality. Although the 500D weighs 5g more than the 450D at 480g that is due to internal changes rather than increased bulk.
Those internal changes are numerous and extensive. The headline feature is the new sensor, the same powerful high-speed 15.1MP CMOS unit as used in the next model up the range, the semi-pro EOS 50D. The 50D was praised for its excellent image quality especially in low light, so this certainly bodes well for the 500D's performance. Also borrowed from the 50D is the superb three-inch 920,000 dot monitor and the powerful pop up flash with an ISO 100 guide number of 13.
One of the few components retained from the 450D is the autofocus system. It has nine sensor points, with a central f/2.8 cross type sensor. It's not a bad system by any means, and operates quickly and accurately even in low indoor lighting, but it does sometimes hunt around a bit in lower light. Compared to the D50's AF with nine cross-type points, or the 11-point MultiCam AF of the Nikon D5000 it does look a bit limp. The 500D has no AF assist lamp, but if the flash is popped up it will strobe the flash to provide low-light AF assistance.
One component that deserves special mention is the viewfinder, which is very large and bright and certainly on of the best in its class. It has a nice bright data display along the bottom, and the nine AF points are indicated by small but bright LED points. The viewfinder has a good wide range of dioptric correction for those of us who wear glasses, and a soft removable rubber cushion. Apparently there is an eyepiece extender available too.