It works really well and works as intended. The ability to manage the OTR keys is nice. Reviews indicating issues with backgrounding should know that this is an iOS limitation, not a limitation with this app.
The chat clients that do not have this limitation typically work with a server-side component that sees the messages (Beejive comes to mind). Of course for a privacy focused app this is not an option.
Gepeto42 about ChatSecure Messenger, v2.2