Interesting. I tried this today and had no problems for a while but then I suddenly had a strange thing occur where the menu stopped using the ControlAdapter and was rendering as tables. I tried rebuilding the whole solution but the problem would not go away until I removed this change from my Web.config.
I've put it in there in comments with a link to the blog post about that setting, so people can use it if they need to, but due to the problem I encountered I'm reluctant to make that the default.
One other thing that is helpful is not using the debugger unless you need to step through the code. You may not be doing this but a lot of devs tend to always run in the debugger by clicking the play button to launch the app, but this is not needed unless you really need to set breakpoints and step through the code. Most of the time we don't really need to do this, we can just compile and then right click the /Default.aspx page and choose view in browser, it will launch the VS web server, or if you have IIS configured you don't even need to do that, you can just open a browser and navigate to the site. Loading all the projects up in the debugger is a much heavier and slower process, of course we need to do that when we really need to step through the code, but we don't need to do that to make a small change and see if it worked. We can just build and refresh the page.