Well, I'm not huge goat lover, but I have to disagree about the smelly, never shut up part. All creatures tend to stink if cared for poorly, and hungry animals tend to holler about it. Care for them decently on a regular schedule and they're fine to have around. Pushy...but not smelly or hollering all of the time. They even handle being hungry without hollering about it if they're fed on a fairly regular schedule.
Coccidiosis usually goes hand in hand with crowded, unsanitary conditions as its spread through ingested feces. Though coccidiosis is species specific, and it seems that just about everything can carry it, from cockroaches to cattle...this is the part that would give me pause about your friends goat.
Our horses have their 'bathrooms'...those neat and tidy areas they do their business in. I've noticed over the years that even the horses I've babysat for friends or neighbors will use those same spots for all of their droppings and urine. Ours have 4 different areas they use in their pen and about 8 or so in their turn out area. That leaves them lots of fresh clean ground for running, playing, sleeping, rolling etc. Even our new horse started to politely go to one of these 'bathroom' spots by the end of day one here.
Our goats on the other hand go everywhere. They jump into raised feeders and potty in them. They'll stand on top of a slow feeder box and go potty in it. They go wherever and whenever the need hits them. They do make fine companion animals for a horse, but I think I'd still refuse a goat thats ever come down ill from it.