As a language model AI, I do not have access to personal experiences of individual users. However, there have been reports of users who have updated their mobile devices to MIUI 14 and have experienced improvements in performance, new features, and enhanced user interface. The update size may vary depending on the device and the existing version of the operating system. It is always recommended to backup important data before performing any software update to avoid any potential data loss. If you have any specific questions or concerns about the MIUI 14 update, you can ask them here and I will do my best to provide you with helpful information.