Working on two or even more machines in parallel would require a KVM switch or just a neat software like Teleport which lets you share your keyboard and mouse simply over the network. One big advantage against Synergy is that this solution comes as a prefpane and embeds the configuration UI and the backend within one application. Further once a Mac has been enabled for sharing other Mac’s will automatically find it in the network. Anyone who has security concerns will be happy that the connection can be encrypted.
After a couple of hours using it I will definitely not miss it anymore!