Owned (still have it) Profilux IIex and switched to Apex about 2 years ago. Apex is much easier to manage and expand. The GHL is a solid workhorse, no question about it. It just didn't have the bells and whistles that the Apex, or newer controllers have.
Just a update on this Issue . I have purchased GF Signet from Bill Wann at Aquarium Engineering. After all the issues that I had with probes not reading correct. I met the owner of ghl at the rap show. After going over the issues we came to the conclusion that my power supply didn't have the three prong plug going into the wall . There term is earth ground. After 4 years of chatting with Michael a $15.00 fix.