Per my previous post, I don't use (cannot figure out how to use, nor feel the need to use) the MCV scenes.
Yes, slow. Sometimes fast, but mostly slow. I don't know where the delay comes from but I *do* believe the plugin dies periodically as originally reported by another poster, so like them (earlier poster) I added a repeating (every hour) schedule event to restart the plugin. I actually created an action item to do that, then have the schedule execute that action item. Then, I also added a "reset plugin" button to my "Doors" control page. So if the lock seems to take "too long" to respond (i.e. it appears the plugin has died) I press the button, wait 15 seconds, then try again.
There are too many moving parts involved (as far as I can tell) for me to try and figure out where the delay or failure occurs. For me, for now, the work-around (reset plugin) and patience prevail. I dream of having enough time to really figure it out!