I bought this keyboard last week, and in my opinion this keyboard is FAR better than the G915 TKL - which I have owned for a couple of years now. Of course the materials are (in theory) better / more premium on the G915, but the stiffness of the base and feeling of the keys, etc. is much better on the G515. Also, the keys are, as far as my jugdgement goes at least, not slippery.
I should add that I strongly prefer low profile keyboards, and prefer Apple's Magic Keyboard for typing - I'm a software developer during daytime. The G515 is the closest to a good combo for typing and gaming I have found, so far. And, no, I don't need the numpad, I strongly prefer without - the mouse can be much closer this way and I seldom type in large quantities of numbers. There are separate numpads for that.