I had Norton on the old laptop i used (my parents) and it was slow (i think 2004). I now have my own laptop and use my parent license (they have a 3 computer license) and it barely affects start up time and i don't even notice it is installed. When i brought my laptop, it came with Mcafee and it was dreadfully slow and used to cause my laptop to stop responding all the time when i did something.
If i didn't get Norton free i wouldn't probably use it but seriously, it is not as slow as you lot make it out to be now. I am guessing you haven't tried Norton 2010? On the old laptop, AVG free wasn't much faster then Norton 2004 and I had a few problems with AVG which is why i would probably never use them again.