I have a custom built PC. It has Windows XP and I am running Cubase as my DAW platform. The hardware is based on an Intel dual core processor with 4GB of RAM. Absynth works perfectly fine on my system. It is installed in the VST format. The CPU efficiency is very good. Even when it's playing a complicated sounding synth part, this program never seems to cause more than maybe 3% of my CPU overhead to be used. Compared with other synth plug-ins that is very good. It is very stable, it hasn't crashed.
I got Absynth about 6 months ago even though it's been out for a long time. I had been using other synths for a while and I wanted to try out something new that is more customizable. That is really the key word with this software - customization. The amount that you can edit sounds is incredible. You can basically build up your own synth sound from scratch with the tools that you are given. It is a little bit overwhelming, so people new to synthesis will probably want to stick to the presets for a while (which all sound very good, by the way). But after getting the hang of it, you can start to build your own patches. If you are into customizing your synth sounds, then this is the program for you. Highly recommended.