If the 600 or 900 is your first ebook reader, you don't notice it. If it's not, you do.
E-ink company are currently working on a touch sensitive layer UNDER the e-ink screen, to avoid this problem.
Also Amazon bought Touchco
http://www.engadget.com/2010/02/03/a...th-kindle-div/
now that the Ipad has surfaced they are suddenly interested in touchscreens!