Like all Blogger features, newly launched, it's got flaws and design omissions. However, it's got a few improvements too. Right now, it's available in Draft Blogger, with the familiar Classic GUI available in Production Blogger.
You're under no obligation to start using it immediately. Like all Blogger upgrades though, it will become the production version eventually. Right now, as it's in Draft Blogger, everybody is asked for feedback - and what you report, now, will help Blogger make a better product.
This is the best time for identifying, and reporting problems. If
- You don't at least try the New GUI out, while it is in Draft status.
- Some key detail requiring improvement, that you might observe, goes unobserved and un reported by you.
- The New GUI goes into production unimproved, because you didn't report the improvement needed.
- You later find that the new GUI is not to your liking.
For more detail about this major step forward in Blogger blogging, see Roberto's Report: The New GUI - Blogger in Draft - An Overview.