Here's my trip report from a Rainier hike last August (big snow year):
I used Inov8 295s and liked everything about them, including the tread pattern. This hike was about 78 miles over 4.5 days, 18K elevation gain, and incorporated big chunks of the WT. Several years previously, I hiked the whole WT wearing leather boots and carrying more trad. pack load. Had knee problems starting the first day, and continuing the whole trip. With trail runners (including Inov8) and a light load, I've never had knee problems.
I wouldn't hesitate to hike the complete WT in trail runners.