what makes an app "feel warm"?

As posted on twitter...

asteris: Twitter crashes becoming really obnoxious of late; I wonder if outages are due to DDoS attacks. Reliable citizen journalism medium it's not # KCorax: @asteris Annoying indeed, but at least twitter feels warm. Jaiku had this kitchen/surgery feeling to it. #

KCorax is to the point. But what makes an app "feel warm"?