60fps isn't slow motion at all until you deliberately slow down 60fps footage in order to get that effect. The video I posted before was 60fps slowed down to 24fps using video editing software, that's how he got the nice smooth slow motion effect.
4k is absurdly high resolution though. I wasn't aware any of the GoPro cameras could do it. I looked up the Hero 3 and that's 3996 × 2160 instead of 1280x720, thus why you only get 15fps. I can't see 15fps footage at 3996 × 2160 being very useful for anything, really. Especially for slow-motion shots, since that isn't actually slow-motion, it's just low frames per second so it appears slow, but won't look anywhere near as good as 60fps footage slowed down. There aren't even displays that can play 4k video available to the average consumer yet.
I'm sure seeing a lot of GoPro footage on TV now, more all the time.
I don't think the 4K is of any use to the consumer market (certainly not to me) but that edition (H3 Black) is also capable of 1080p @ 60fps and for really nice slo-mo it can do 720p @ 120fps! That and the better lens, etc. made me buy one. It's really a nice tool for the money.
Congrats to the OP on the 60D. Nice to see the enthusiasm, sounds like you are going to have a great time finding out what a good DSLR can do!