I purchased a pair for a week long paddle trip last June as my old reliable Teva sandals were about shot. The Keen's are very comfortable and protect your feet. However, they nearly drove me crazy with all the gravel and mud that gets stuck inside when you get in and out of the canoe. I nearly always had to take them off and rinse in the river before I could continue paddling. The Teva sandals did not hold nearly as much muck and generally I could rinse without taking them off.
I still like the Keens just fine but you should be aware that they trap guck if you step in it. The toe protection is worth the aggravation, in my opinion, however.
One additional note... I also have a hand build cedar strip sea kayak that I built over the winter. I planned to wear the Keen H2's when paddling but found that my size 13 Keens are so large that they just won't fit in my kayak. I was forced to buy some thin paddling booties just to get my large dogs inside. If you have big feet, the H2's might not fit in your kayak...