This weekend while camping, it rained incredibly hard.  Noticed we got some water in the camper near the slide.  
I attributed it to user error.  We were on a farm field and I didn't bother leveling side to side much since it was within half a degree.  
Since I don't have a slide canopy, the water will sit on top of the slide and eventually make it's way in if you aren't pitched enough.  Usually if I know it's gonna rain, I pitch it slightly to the slide side to prevent intrusion.
No big deal, just ran the box fans on the carpet to dry it out and in a couple hours it was dry.  
So, slide issues but self induced :) Wouldn't stop me from getting a slide in the future.