I've been using Ubuntu and variants for a long time now. I find lubuntu is ok and small in terms of size. As for older computers, I must have some really slow ass hardware, because even lubuntu is kind of slow on some of my hardware. I stick to standard ubuntu on my desktop just to see what it's like, but prefer xubuntu because I prefer the DE over the gnome crap. I'm used to the more standard keystrokes and shortcuts that you see on windows and the IBM standard which gnome wants to ignore. It's also tough to customize gnome to how I like to do things.