Looks like you're not the only one:
Knockout.js incredibly slow under semi-large datasets
from stackoverflow
My company had 6 developers working on a .NET MVC site using knockout for almost a year. The result is a disaster. When the first page loads, 90 js files (e.g. telerik, jquery,jqueryui, - lots of plugins, etc) and 30 css files are downloaded. It's a nightmare. I've only made a superficial review of knockout and the Google equivalent - AngularJS. It appears to me, Google's got MS beat. I don't like the fact the knockout sits on jQuery - while Angjular handles AJAX internally.
Anybody seen a large, successful site using knockout?