When I got my very first 7 16 week olds years and years ago I too thought they were absolutely FUGLY! YUck, who's dirty trick was it to stick such an ugly head and neck onto such pretty plumage! And the noise when I let them out of their pen the very first time.... OMG, they were CHI-CHI-CHI-CHI-CHI squawking at everything, made my dogs howl and my horses run, lol. My neighbors WAY up the hill even called and asked what all the racket was, lol.
I'd say it took a year or so for them to grow on me... I think about the time a couple Hens hatched out some adorable clutches of keets for me... that was it, I was hooked. Not to mention the tick and snake population on my acreage was significantly reduced, bigtime, and rather quickly. So yah, I was hooked. From then on I have not had less than 30 of them running around on my land ( and right now I'm close to 100, lol). I'll never not have Guineas, ugly or not, you get used to it (especially if you have turkeys like deb mentioned, lol) and they really do earn their keep!