This thread is way more entertaining than I thought it would be! I've read through half so far but I want to get my post in before DD wakes up...
I voted yes, but I'm of course in the "Only if nobody's coming down" camp. DS has been climbing up the slides for years and I think it's super. He actually makes up games in our backyard that incorporate him running across the yard and up the slide.
DD just learned to climb up the slide the other day and I'm so flipping proud of her.
She's been watching her big brother do it and she's finally got enough strength and coordination to pull it off. I love how pleased she is with her accomplishment. I still make sure I'm standing there with her because she's slipped a few times, but to be honest I'm more confident in her ability to climb the slide than the ladder.
This thread has reminded me of an incident at a playground. The mall near our home has an indoor playground near the foodcourt and I took DS there one day. It was fairly quiet with only a few kids playing and he was climbing up the slides. I was keeping an eye on him to make sure he was being safe and considerate of others. A mom of a toddler went over to DS and insisted that he could NOT climb up the slide. The empty slide that nobody else was on.
: It was one of those moments where I wish that I'd said something but I was too stunned at the time.