ShapeShift started to use mixin and had to stop due to problems.
Coming soon there will be a service that allows BTC -> XMR transfers supporting mixins 3+ by default and payment IDs.
This is a positive development!
And this.
https://shapeshift.io/site/blog/2015/09/24/new-tool-shapeshift-skeleton-allows-site-exchanges-video
Quote
Please welcome ShapeShift Skeleton to our suite of merchant/user tools! Skeleton enables any website to allow instant purchase or sale of digital assets and cryptocurrencies. The tool allows for exchanges to be made by a sites users without them leaving the site.
Skeletons code is free and open-source and offers a template that is customizable, giving integrators the ability to brand the tool with their own assets and colors.
Why would you want to have this offering on your site? For all cryptocurrency-related sites, this gives your users instant ability to purchase the assets you support without having to take an additional step of visiting an exchange to make their purchase. Additionally, you remove the risk of the person leaving your site to make a purchase and never making back to your own website.
Skeletons code is free and open-source and offers a template that is customizable, giving integrators the ability to brand the tool with their own assets and colors.
Why would you want to have this offering on your site? For all cryptocurrency-related sites, this gives your users instant ability to purchase the assets you support without having to take an additional step of visiting an exchange to make their purchase. Additionally, you remove the risk of the person leaving your site to make a purchase and never making back to your own website.