If you are a low-end Linux enthusiast, I would also recommend the Trinity desktop. Just as MATE is a continuation of GNOME 2, Trinity is a modern version of KDE 3. I was quite surprised how light and functional it is.
If you want to give it a shot in a VM, the Q4OS distro includes it as a default DE option. If you really want to be impressed what can be done with little RAM, try the 32 bit version of Q4OS.
If you do try Haiku, use Fallon as the web browser. You will have a much better experience than the other Haiku browser options.