And to think that my friend was using a 2009 macbook with 2GB of RAM and a 128GB SSD until a few months ago. Now it has 4GB of RAM, and while doing development work (Eclipse and another copy of JVM running) and having two accounts logged in, both with Safari open, the swap sits unused, and there's a few pageouts but not too many (a couple thousand per hour)... And this is on Mavericks, which has higher resource needs compared to Snow Leopard.
My kid uses a MBP of similar vintage with 8GB of RAM. It works great even though I'm can't seem to bother to replace the mechanical hard drive with an SSD. On Mavericks you essentially either need an SSD or lots of RAM to cache the underperforming hard drive. Mavericks seems to access the hard drive in such a way that makes mechanical drives seem very sluggish. Minecraft, multiple instances of youtube, etc. -- all work great.