We're not using Yarn at Tilde yet, but I've been using it on Yarn itself and when working on Ember packages, and it's worked well. As far as performance, we have good benchmarks tracking yarn's performance in a whole bunch of different scenarios (https://yarnpkg.com/en/compare)

Ok, didn't realize he worked on it. Bundler is great so that gives me some hope for Yarn. But in general I think its more stable in the long-term for projects to use open standards instead of vendor solutions for browser package management.

I can understand this sentiment in general, but don't think it applies here. npm is also a private company, and this does work with their registry. There currently isn't a vendor-neutral standard to follow.