I had only an occasional photo with a digital compact camera. However, when I accidentally by a friend the 400D held in his hand and had some photos, I wanted to have this camera and since I seduced by the sight of this camera every day! ;-)
I use mostly the Programmed Auto (P), since you do not have to set a lot here (but you can) to shoot brilliant pictures (two pictures I uploaded here at customer images). Especially shooting with little light can be with ISO 1600 and no flash quite handsomely.
About the 2.5 screen, the image is displayed immediately when you have caught it. The duration of the ad preview the way you can adjust the menu (2, 4, 8 seconds, or keep). I have it at 4sec. set, which is usually sufficient.
That I do not have the beautiful display can not use as a viewfinder does not bother me because it saves battery power and I think that the response time of the display anyway insufficient to show fast movements.
Currently, I have about 1280 pictures with the Canon and the kit lens (18-55) shot (about 200 with built-in flash) and the battery I had in between only two times recharge. In my opinion, is more than good! Certainly, the photos do not compare with the kit lens with those of professional cameras and expensive lenses. To play around for starters, it is to use all the time very well.