I have ran mini spools, full spools,and welded diffs. They will wear tires ALOT faster. The rear does brake loose prety easy, espicaly when wet. Any slow, tight turns will result in churping tires. Driving on ice is NOT recomended, atleast I had a hell of a time. Taking off when turning needs to be done slowly, auto trans make it alot easier, handling wise. Driving on the road will punish your axles. I realy dont recomend this for road, or atleast very little road time.
Now the good. Great traction off road. Steering returns to center on its owne. Cheap.
IMO and experiance, a spool is realy only suited for off road use. On lighter trucks it doest cause as many problems but Broncos are realy to heavy in the rear and it puts alot of extra stress on the axles not letting the tires spin as easily. I have ran the spools for years in several diffrent rigs. The currant Bronco I wheel now had a spool and I removed it due to all thats been stated above because i wanted something that would be street friendly as well. I decided to go with a Detroit Tru-Trac and for me it works great and on the street you dont even know its there unless you hammer down.
Thats my 2 cents. But search around, there are several threads on this. Good Luck.