IK Mulitmedia are currently giving Custom Shop owners the chance to grab, for free, Opto-Compressor for T-Racks and Modern Tube Lead Head & 4x12 Cab for Amplitube.
FREE Opto-Compressor: Optical compression has a special sonic character and this analog-modeled processor faithfully recreates that particular (and extremely musical) “movement” that characterizes only the best opto compressors. An important characteristic of optical compression is the total absence of distortion and coloration during gain reduction, and you can expect the same character and performance from this digital recreation.
FREE Modern Tube Lead Head and 4x12 Cab (based on the Mesa Boogie® Dual Rectifier® and matching Celestion loaded 4x12 cab). Modern Tube Lead models one of the leading amps for the hard, driven rock tones made today. Capable of searing leads, a thick rhythm sound and heavy crunch, this amp creates a modern rock tone that is hard to beat.
That kind of covers it - more here