On 2.8.3, the latest version of this plugin alters the image uploader so that it appears that css is broken after uploading and that there are some other conflicts.
When activated the browser uploader is the default, but the file uploads. The page after the upload has tons of excess space and fields and text are not in the correct place as if css is broken. If using the flash uploader, it uploads, but does not proceed to the image option fields.
I have no idea if there are plugin conflicts or if it is just Smush.it and WP. However, deactivating Smush.it returns the uploader to normal.