You can setup your settings on your Eris the right way to where you don't have to enter your password everytime.. and it's just the way OS was built... I don't see how it would be too much of a problem though, So you have to touch the screen one extra time before entering your password..
In my opinion, I like it better this way, because it prevents me from hitting buttons when I don't like to.. Also, I'm not sure if your HTC Touch or any other phones you have had had a proximity sensor in them to turn off the screen when its near your face.. Seems to me that HTC took time in making sure people don't accidentally touch keys while on a call.