iOS 11.3 is not just an update to fix bugs, but there is actually new functionality. If you go to Settings> General> Software update on your iPhone you can install the update. settings and then to general and afterwards The most important new functions are listed below.
Apple has also adapted iOS to comply with European regulations. Soon you will therefore be able to completely remove your Apple ID online and / or download the data.
In the next update of iOS 11, specifically named as iOS 11.4, you can expect AirPlay 2 and iMessage may come in iCloud, so that you will always retain all your messages. In addition, software stability is being worked on. iOS 11.4 is expected in late May and early June.