I've never treated any of my MJs, or my Balenciagas for that matter, with any rain repellent... but then again, it doesn't really rain where I live. This past rainy season my bags held up really well with no water spots despite the lack of treatment.
I do condition my bags with Apple Garde when they look thirsty, but other than that, I only clean them with alcohol/lanolin free baby wipes. I tried using Apple Garde cleaner on my Maroon ZC once, and to my horror it lifted up a lot of color. I've never used it since.
The MJ SAs don't recommend treatment because supposedly the leather is already treated.
I've also tried Cole Haan conditioner/cleaner with success, and I've heard good things about Wilson products.
I've read that Coach cleaner can leave a residue on the leather which can turn yellow over time.