2.1.0 might be production ready for small shops and/or the US market, but as soon as you have thousands of products and multiple languages and storeviews to support, you will run into very nasty bugs. and then there are the performance issues that come with mid/large-sized shops.

we're currently in the process of migrating a CE shop with around 20k products in 2 languages from 1.9 to 2.1 and it has been very very painful so far. our next EE shop customer will have 70k products in 2 languages and 4 store views. we won't be migrating them anytime soon as we do not think that the current code base is even close to stable.