I really think this comment is overblown. Until 2-3 months ago, I was using a T400 from 2009. It had 4 gigs of ram. I could happily hum away with Firefox with like 30 tabs open, Chrome with like 10 tabs open, IPython notebook chugging away, and Grooveshark/Flash burning up my cycles. While it certainly was not as smooth or as fast as I would have liked it, it certainly never really held me back.