Personally, I'd spend the money and have someone else take the chances...

Oh wait, that's what I do! $35 a few times each year!

They make boots for walking on roofs. Here's one brand.

Here is a link that might be useful: http://www.cougarpaws.com/

Don't know about nikes specifically, but I was surprised to find that that my adidas slipped so much much compared to my steel-tipped work boots with what I thought was just black rubber. It says "Carbo-tec, Oil, heat, slip resistant" on each sole. Even though the soles are worn out, they still hold well. Can't recall the brand, but I think they're sebago's.

There's a shoe catalog and web site called "Shoes for Crews" that specializes in non slip shoes. My son works in a restaurant and says that they really work.

bus_driver-
I don't bounce as high these days, either, so I'm also reluctant to do this anymore. I have a two story house with a steep pitch, and this year I made a gutter cleaner out of 3/4" copper pipe. It's got a hose fitting on the bottom, and a couple of fittings at the top to make a U-shape and ends in a male hose fitting that takes a small jet shaped attachment. I put on my wet gear, hook the top end over the gutter edge, and blast away. If you want to get fancy, you can also put in an on-off valve at the bottom end.

How often should homeowners consider scheduling gutter cleaning services, and are there any signs that indicate when it's time for a cleaning?