The performance hit was due to database work they were doing on the instance. Now it's a lot faster. The latest announcement reads as follows:

    We've completed our first phase of database clean up, thank you for your patience.  The impact on performance was heavy, but it was a necessary step.  All active users and their posts, profile, connections and media will be migrated to the new servers.  Once that has been completed, any remaining data will stay online for further migration and clean up.  Our instance is nearly 10 years old of constant daily operation, but we ran into a migration wall which held us back on 4.1.x.  Now that it is deprecated, we will do our best to jump to the latest version rather than migrate through.  Your support and patience has been greatly appreciated.