[VINMAN]

had one intsalled in my grand cherokee (normaly something I would do myself, just didnt feel like doing it...) One of the top of the line ones intstalled by a very reputable place. all i have to say is after a few months nothing but trouble with it. Battery would be drained after sitting 2 days. lights would flash on and off all different times. door locks screwing up. No controls on the steering colmumn working. Decided to try to fix it. Crawled under the dash, took a look, the wiring was trashed. About 20 gutter taps all over, wiring cut , fuses spliced in.
Ended up cutting everything they did out. and resplicing or replacing that section of wiring. Ive seen a lot of other people have nightmares with these things. But also some trouble free. Like Fred stated, a lot of important wiring gets cut and reconfigured. Real easy to screw it up.
The ones I put in my Bronco, and fire chief's vehicle myself, never had a single issue with them.