Yeah, 8GB should be a minimum standard nowadays for usability. I run out of RAM fairly often on my Bay Trail Atom dual-core laptop, that only has 4GB on it, as well as my AMD APU quad-core laptop, that also only has 4GB installed.
Also, get an SSD, if you haven't already. That can largely mitigate the need for more RAM, within reason. (If you're actively "thrashing" the VM pagefile, even with an SSD, you're going to see slowdown and pauses. But at least the machine won't lock up solidly unusable, like with a HDD.)