Performance has always been an issue with this plugin. The biggest resources waster in repository, quite possibly. I run a site with 300k uniques, 3+ Million pageviews a day, on a powerful dedicated server with lots of RAM and 4 SSD driver in RAID 10.
My MySQL connections and CPU usage are through the roof. Disabling the plugin brings them down significantly. The plugin is clearly programmed for splog users with little to no traffic, but many of them. Latest version is by far the greatest disaster, since it increased load even more and started creating thumbnails of each uploaded image but since I don't run a splog, I have tens of thousands uploaded each month so the plugin hard core overloaded the system. It will take me a long time to undo it and recover from it. Definitely looking for an alternative.