Thanks for these links. I ended up grabbing a routerboard 450G because they look like a really nice piece of kit. Probably overkill for playing around with routing, but I couldn't help myself.
You can install OpenWRT to compare although it looks like installation is a slight pain: http://wiki.openwrt.org/toh/mikrotik/rb450g - it's probably easier to install as a metarouter if you're just playing w/ it: http://wiki.mikrotik.com/wiki/Manual:Metarouter