I had hesitated for quite a while to take the plunge to 5.7, but it didn't take long to get my bearings. I'm still not a big fan of Redactor, I feel it has it's limitations to the end user, but that isn't necessarily bad since giving clients too much editing/design free reign can break the design. So I'm 50/50 on it at this point and will have to see if the client update requests poor in when they can't do certain things they're used to in 5.6. Layout grids are great, a little buggy to modify depending on what's on the page, but overall easy to implement and work with. I didn't use it, but it's nice to see the return of an image editor. CSS and JavaScript caching ended up breaking some of the blocks, so I have it off. I'd like to see this addressed in the future. Specifically, the Quicktabs addon didn't like it. The front-end design capabilities are nice, but once again, if you get an overzealous client with Admin access, it's only a matter of time before they add their touch and break the design. Overall, I'm sold and will be working with 5.7 moving forward.