I'm not running the Oli Larkin Quadmix plug-in any longer at home since I don't have a system that will run it anymore. My old computer was a Hewlett Packard Pavilion dv8000 Notebook with a 3.0 Ghz processor and 2 GB of RAM, which I used to run Cubase SX 2.0 and later 3. I didn't have any issues running this plug-in on this system and would be surprised if users did have issues with it.
While I never used the Oli Larkin Quadmix plug-in too much when I had it, it's still one worth having around if you're dealing with synth related activities. It's not going to be needed on anything close to a daily basis (of course depending on what you're trying to do), but it came in handy a few times for me. It's nice that it's free of course and does give you a good amount of control considering this. Not everyone will have a compatible system, but for those who can get it, it's worth having Quadmix and Quadpan if you're dealing with routing virtual synthesizers at all.