Man, I was such a wanker back in those days.
Although it's been a while since I played it, it's definitely worth playing. It's basically QFG1VGA but kinda adult, just because it's called QFG4 1/2 it doesn't mean it comes after QFG4, really, it should have been called QFG2 1/2 or something. (Though, there are references to other QFG references.)
I think people are way too conservative about this sort of thing, at least in one sense.
Why all this pontificating about whether or not to play it? By all means, say you don't like it and won't play any further IF you've given it a go and decided it's not your kinda thing, but I'm at a loss to understand why people keep asking the question, "Should I play it", except that people are basically prudes and conservative. Which is probably true of our (the Sierra) community to a large extent, but conservatism and whether the game's any good is two separate things.
I never completed it due to time issues, and partially because I was a little offput by some of the adult themes. But I was a 15 year old virgin at the time, so some of the more adult themes were maybe over my head and confronting, at the time. Looking back I think the game (at least, as much as I played of it) was hilarious and actually, much funnier and better than the original, dreary, QFG1VGA remake.
And to be fair, if you look past the sexual content (of which there isnt much, it's all centered in one or two places), it's really just a usual sort of QFG game (like 1VGA and 3), except more spoofy of itself, rather than of RPG's/movies/etc. in general. It fits neatly into the QFG series, and to be perfectly honest I think if some of the more adult scenes were cut it'd be a QFG fan's favourite, and not 'hidden behind closed doors' and whispered about, at least, quite so much.
Anyway. It's an excellent fangame, what I played of it anyway. Recommend, 2 thumbs up.