I'm currently trying it out myself.........first impressions are good.
For a free program it has automatic updates and real time protection along with a scheduled scan.More than you can say for the other three.....unless you pay for them.
I'm not sure it's detection rate is quite as good as the other three you mention...particularly SuperAntiSpyware which I think is extremely effective( I too have all three on my system)
Spyware Terminator also has a decent set of utilities.
By far the best feature is the extremely effective real time monitor which has HIPS as well.
I also find it does not impact on my systems performance ....unlike Windows Defender which could cause a noticeable delay in opening programs etc after my pc had been running for a day or so.
It does use a fair bit of RAM though...currently peaking at 53MB although that is whilst running a full in depth scan.
It certainly works well alongside my preferred firewall (Comodo) and current free AV (AntiVir Personal Classic).
Well worth trying in my view.