I peeled off the tape on X3REX, my modified Prusa i3, then coated the glass with ABS dissolved in acetone. I set the bed temp to 100 C, put an enclosure around the printer, and added a 4mm brim to the slicing profile. The results were great. The bottom surface was really clean and smooth, no warping, and once the bed cooled, the parts just fell off the glass. With Kapton tape, I usually had to pry the parts off which can damage parts or hands trying to do the prying. I also peeled the tape off of my Airwolf3D v5.5 and had good results there too.
The parts I printed were of uniform thickness, so I may be jumping to conclusions about the effectiveness of this method, as parts with varying thickness have more of a tendency to warp. I'll let you know if things change.
Kapton tape works great, and I think it's especially helpful when you first get into printing since you have less warping to deal with. But once you get the basics down, I believe you can do without this expensive consumable.