Bookmarks: In VS 5 they seemed like a great idea but I ended up not using them mainly because they didn’t persist between sessions. E.g. If you closed a file that contained bookmarks they would not be there the next time you opened the file. You also could not move between bookmarks in different files etc. and I stopped using the feature.
For years I would kill the bookmarks toolbar whenever I installed VS. It took me years of using VS 2005 until I noticed that the bookmarks feature had actually been greatly enhanced and I use them on a daily basis.
Have you ignored Visual Studio features and later discovered their value?
It wasn’t so much ignoring VS features as it was being ignorant of them, but for a while I didn’t use custom project/item templates and code snippets, even though there was significant boiler plate code at my last job that was easily fixed by using these. I used the default templates for a while until I realized I could customize them for our application, and it’s saved me loads of time since then. Code snippets I used to a lesser extent, but I do find them useful for smaller bits of code.
The other “feature” I find infinitely useful these days is “Delete all breakpoints” (CTRL-Shift-F9). I used to keep all of my breakpoints around, and they would persist in each solution…but it would 1) slow down VS load times, and 2) disrupt my debugging behavior by breakpointing in sections of code that I didn’t need to breakpoint in anymore. Instead of manually removing them, I got into the habit of removing all of them, and then placing a few key ones around code I really needed to test. This was more contextual though – initially having a ton of breakpoints was useful to learn the codebase, but once I was familiar with it, isolating bugs was a lot easier without all of the breakpoints hanging around.