I use it on my Z-Force S and it works well. The trick is to do it from day one while the underside is still pristine and then after every single mow, starting with the side furthest from the chute then going to the chute side. Like the manual says, two minutes on the far side, two minutes on the chute side, then two minutes to dry.
If the nozzles clog with grass and debris it's easy to clear them out from the top with a tiny screwdriver. It doesn't happen often but if it did, I'd probably find some rubber or plastic caps to put on them.
I've been mowing damp and sometimes wet grass for several weeks now so out of curiosity, I went out and cranked the mower up with my MoJack for an inspection just now. Every bit of the deck underside is clean as a whistle except for a very thin coating of grass debris on the bottoms of the spindles, and an eight inch diameter circle around them. I was glad to see that because it means the water is slinging well away from the spindles rather than washing the grease out of them from underneath. It doesn't look like I'll have to scrape the deck more than once every two or three years at the very most, so for me the deck wash system is a big hit. Six minutes of my time for a clean deck that will perform as well as it can each time I mow seems like a fair deal to me.