There are different kinds of skins available. Some are clear and thin, and then some are texturized and thicker (leather skins, carbon fiber skins etc.). Obviously it adds to the thickness of the iPad. Furthermore, the iVisor XT is a thicker screen protector which has fake iPad borders (black or white). So that's more added thickness. Obviously I was worried about if it fitted the groove or the channel of the Zaggkeys (or if it affected the viewing angle). Anyway, I now have all of the above-mentioned accessories and can say that not only does the iPad fit in the groove but the viewing angle is still good. I can also say, regarding the stability issue when iPad is in the groove, that I couldn't get the iPad to fall off no matter how I tried. I tapped the iPad hard, I tilted and moved the Zaggkeys but yet the iPad didn't fall off. One factor here could be the thickness of the device you place in the groove. Perhaps people with most problems with stability are using a narrower, lighter iPad (iPad 2). Moreover, a customer on Amazon wrote that perhaps the added thickness from his back skin and screen protector fastened the iPad better in the groove. All in all, I'm very happy about the Zaggkeys Pro Plus.
Regarding the backlit keys... Obviously many people buy the Plus-model for its coolness factor. While there can be situations where I would benefit from the backlit keys, I doubt I would be in them for more than once or twice a year. On the other hand, buying directly from Zagg let's you use coupons to get the price down.