Muv-Luv is the only adult game I paid for, via kickstarter, and I'd already played the whole game multiple time by that point, it was more a support thing. So yeah, worth it.
It adds a reason for tension to build without going straight in, it's something people shouldn't do so the buildup can be longer, with one or both party resisting their impulses at first, same reason I like teacher/student and cheating stories.
I'm all about games with mechanics, be it a simple training/daily life simulator like Sister Monochrome type stuff, or deep management games like Free Cities, for VNs though, all you need is choices that matter, maybe affection/corruption points or a minigame tied to the theme of the VN, but...
Porn Games have the major advantage of having a very effective gameplay motivator, fuck all the girls, impregnate them all even better, it's like an extreme version of watching numbers go up in an RPG.
Muv-Luv is very light on the smut (1-2 scenes per routes), but the plot is an amazing rollercoaster, I encourage going into it without knowing anything, the games order is Muv-Luv Extra, Muv-Luv Unlimited and then Muv-Luv Alternative. (Extra and Unlimited are packaged in the same game.)
It...