Eddyflower.com has a good description of the local runs. I lived there for a number of years and the boating could be worse. Spring boating following a good snowpack winter is fun - the Ogden and Weber up in Ogden, UT and the Provo river down in Provo, UT can offer a few weeks of spring boating - April/May. Plenty of runs in Idaho that are 3+ hours away, and the Snake River up by Jackson Hole, WY is great all summer long, and only a mere 4 hours away.
Plus, you're that much closer to the big multi-day rivers - MF and Main Salmons, Lochsa, Snake, etc.
Unless kayaking is the only thing you do, SLC has a lot to offer and is centrally located to a lot of great places and outdoor activities. Four hours in any direction and you can hit all sorts of National Parks (Yellowstone, Teton, Zions, Arches, Canyonlands, Bryce, etc, etc) and other great places.