I had a Jacto PJB16 and found that it worked well, however I wasn't confident that I was applying at a consistent enough rate. It bothered me so I returned the unit and purchased the spreader mate.
Pros: I thought the 5 pressure settings, visual battery indicator, and the in-tank agitation were great.
Cons: I did not like the pace indicator, I found it harder to use than I thought it would be. I also found the sprayer wand to be lacking in quality for such an expensive piece of equipment.
If I hadn't gone with the Spreader-Mate I would have seriously considered the My4Sons M4 Gold Edition. It appears well built and comes with a lot of accessories for not a lot of money.