I bought this camera second hand a couple of weeks ago. This is my first Slr camera and my first impressions are amazing. This camera is a massive step up from the 'bridge' camera that i had before. Although it has alot of the same features such as the mode selection wheel, auto focus feature and short cut buttons, the 450D has a much larger 3" screen and has a full manual mode that allows you to change all the settings such as the iso, aperture and shutter speed. One cool feature this camera does have that most slr's of this age don't is a live view feature. this means that when it comes to tricky shot angles you can press a button and the image you are looking at will appear on the screen, just like a normal digital camera. This feature is hard to set up but chapter 5 of the manual tells you all about it.
depending on whether you buy the body on its own or with the standard lens you should receive a 18-55 mm lens . This covers the majority of all photographs an ameture photographer like myself will want to take, although if you want to further your skills there is a wide range of lenses available, not just from cannon but also from sigma and tamron. Alot of people will say that you shouldn't buy an slr if you dont know how to use it, but you have to start somewhere and this is a great camera especially because this camera allows you to be as guided or as independent as you want so you can have it full auto or full manual. im not sure how this would cope with the more professional photographer but i would recomend it to someone starting out.