Gig Performer is a lot of fun because you get to lay out your own UI if you want. This is helpful because most plugin UIs are designed for studio use, where you've got a large display and one hand on the mouse. Small controls, multiple tabs and tiny labels are not much of a problem in the studio. On stage, you need large controls, high visibility, and minimize use of a mouse or touchpad. This is where GP stands out from the crowd.
But with a list price of $250 Gig Performer is positioning itself with the big boys. Forte is $100 (more for the advanced Producer edition), EAReckon's BloXpander is $73, Cantabile is $69/$199. Forte and Cantabile are more mature and feature-rich. I wouldn't be surprised if GP settles in at a lower price point.
I've just turned my attention from Cantabile Solo to Cantabile Lite. The obvious attraction is the price (free). But so far it seems to satisfy my own needs just fine. I've got it set up with Keyscape, Zebra, Omnisphere and VB3. Next step: configure the touchpads on my controller to select them. If that's possible, Cantabile Lite could very well be my immediate solution.
For those who have purchased Gig Performer, please let me know (here or via PM) how your experience is going. I will be reviewing it in the March edition of SoundBytes, so all input is appreciated.