Been running one on my new rig this year and so far I have nothing but compliments for it. Starts easy and runs smooth from cold to hot. I run the tiller version and coming from my last 9.9 Pro-Kicker I do like the handle in the middle versus off to one side. It has taken a little getting use to the actual gear shift lever versus the throttle actuated gear shift of the 9.9. With the 9.9 being a little cold blooded, it would've been nice to have this set-up on that motor instead of having to reach down and push the neutral button to increase the throttle in neutral. With the EFI, I think the old 9.9 throttle/gear shift would actually be better since it runs so nice and isn't cold blooded. I will also say that if you try to pull start it, they must really have the pull started geared down or some type of compression release because they pull over like butter. the 9.9 pulled over way harder. I always try this just to check as it's kind of a last resort if all the battery's end up dead because of a short or something.
With that said, shorthairsrus, the reason for the 15 EFI over the 9.9 is Merc has not added EFI to the 9.9, she's still a carbed unit. The 15 is only like 18 lbs heavier, has a much bigger alternator that can keep up with charging at idle while remote steering with a power steering of the Verado, and has EFI. The additional thrust doesn't hurt either even though I hope to never really need it. For me, it was all about having EFI. I will say however the kicker is louder than the 350 Vrod sitting next to it, even my wife commented on it, lol.