Some features are still under development. Please see this article.
Although the HTML5 release is still missing some features available on Silverlight, the most commonly used features are there already. That is why the HTML5 interface will be presented to you as the primary interface. This means that when you choose to Login, you will be taken to HTML5, by default. Nevertheless, you will be able to choose the legacy Silverlight interface, during the login process, by clicking the alternative link, if you need any of the features still unavailable in HTML5.
If you are using Frotcom in a language other than English, you may notice some words still not translated to your own language. It is probably something we did not notice before but needs to be corrected (you can use the Feedback link, under the user icon).