In many cases, when you use your up and down arrows on web pages, the web page will scroll up and down a line at a time. Last week, when Google introduced the blue arrows as a way to navigate the search results with your keyboard, it removed the line by line scrolling.
Now, when you use the up and down arrows on your keyboard, the page may jump down after you down arrow enough to hit the results under the fold. So you don't get a constant scroll using the up and down arrows, the only time the page moves down or up is when the result the arrow is on is not in view of the web browser window.
For some in a Google Web Search Help thread, it is annoying and they don't like it. There are other threads with complaints as well. Personally, I think these users will eventually just get use to it and go on their merry ways.
Forum discussion at Google Web Search Help.

Comments:
Davey
12/16/2010 12:14 am
I agree, it's very annoying, anyone know of a fix?
Barkerp3nfo
12/21/2010 08:35 pm
If you hold down the CTRL key, the arrow keys will scroll the screen, but the little blue 'arrow' doesn't move. So if you then release the CTRL key and press the arrow key, the screen will jump back to what ever the blue 'arrow' is pointed at. Not a fix, but a workaround...
Guest
01/03/2011 08:41 pm
No, people will not get used to it. I have stopped using the arrows keys on Google search screens since it has made it difficult to use. My eyes can scan down the results far faster than I can get the cursor to the bottom of the screen in order to scroll it. They have introduced a large usability issue with this change.
Erik
05/08/2011 06:17 pm
Disabling google instant takes care of this as well. I thought about it for a second, and realized that I don't actually like instant any way - too much data.
guest
05/23/2011 08:02 pm
I agree. My eyes can quickly scan the page much faster than the jumping blue arrow. My solution was to change my default browser to BING. Goodbye Google.
janea
07/03/2011 03:28 am
this works!! gosh, the arrow was so annoying. thank you for posting this reply!
Throw Away
07/07/2011 06:39 pm
in firefox, hit 'Ctrl+F'. the point is to invoke the firefox "Find bar", but don't bother typing anything in it. at this point, your up/down scrolling behavior should be back to normal. (Firefox 5.0)
Cc
08/31/2011 09:01 am
I've had a while to get 'used' to it and this is why I'm here, on a blog, by someone I don't know, because I've cracked with the stupid cursor key thingy and because I've now had no choice but to google 'annoying google arrow' and here I am.