WriterDuet keeps getting better, in preparation for the desktop application. I’ve spent a lot of time optimizing performance, and many of the improvements have helped the web app as well. In fact, the web app now loads up to 30% faster (in addition to another ~20% improvement recently), and uses a lot less memory.
Important note: The price of WriterDuet Pro will be increasing to a one-time cost of $69, and that price includes all Pro upgrades (including the upcoming desktop application). Also, a lot of Pro features which have been made available to free users (with explicit notes stating they are Pro-only) will be disabled for non-Pro accounts very soon. To continue using them, I highly recommend you upgrade now for the lower price.