Not really. The difference between 3.5lbs and 3lbs isn't even really something worth discussing when the device will always be resting on something when you're using it. If we were talking about the iPad or a similar tablet then yeah, of course that would be a big deal.
Well, yeah, if your laptop is always sitting on a table and you walk up and type on it without ever moving it, then you really have a desktop and weight is irrelevant.
But laptops get carried, they get held in odd positions while you're moving around. If they're light enough you can hold them above you in bed without your arms falling off. You can sit sideways on the couch and prop them on your knees. At that point, ever 18% lighter is very important.
