I've just installed it and started playing around.
On first open, a lot of the interface was unreadable because VimR seemed to be assuming a dark background, but I use a white background. `set bg=light` didn't fix it. `colorScheme=PaperColor` fixed it incidentally because it didn't find the color scheme and reverted to something legible, haha.
Next, I tried to set the font size for the navigator to something bigger because my eyes aren't that great. Although I can use `set guifont` to set the editor area font, the navigation area doesn't change. Presumably there's some way to fix it, I just haven't found it yet.
VimR looks cool and I really like having the navigator there IDE-style, but it seems like there will be a period of adjustment. Nothing new for someone accustomed to Vim, haha.
The main IDE-style features I've been going without in my ordinary day-to-day editing with MacVim are the autocompletion, suggestion, and hover-to-show-documentation. (I've started using ALE which is helpful but needs some tweaking before it's really usable.) It might be possible to get those with either MacVim or NeoVim, and it would be worth the configuration to set them up if so.
Have you tried coc? Despite the repo name it works with regular vim too and is definitely the easiest way to get completion and other LSP functionality (jumping to definitions, doc previews, error highlighting etc).
[0]: https://github.com/qvacua/vimr