I took a year off. I know what you mean about the feeling slightly stupid now. Since I've been out of the academic environment for quite a while, I worry too that I'll be a little rusty when I get back. I've been working close to full-time, so I've been pretty busy with that. I also feel like I spent tons of time working on my applications. However, this year I committed to spend tons of time reading all those novels that were harder to read in my free time during undergrad. Since I'm an aspiring Victorianist, I've been reading lots of giant Victorian novels this year, as well as a few critical books. I think the habit of reading is important to keep up, even if you aren't necessarily writing papers about the books you read. Sometimes reading through a novel once helps you to be more detailed and attentive the second time through. I've also taken my undergrad thesis and made a pretty detailed outline of how I want to expand it and improve it. I'm also planning on reading a lot of theory this summer, just to refamiliarize myself with it and also to think of possible teaching angles. The other thing I want to do is look at various journals and see which ones I would like to be published in, so that when I write papers, I have an idea of direction. I sound really overachievey, but I guess all this time out of academia has allowed me to accomplish things I couldn't have done while still in school.
I'm not getting stressed about it, though. If I don't get everything done, I'm not going to worry about it. I know that time off will help me to be able to dive in when school starts. I'll have energy, I won't be burnt out anymore, and regardless of how much I have prepped in my time off, I know that I'll still have the research and writing experience to get started. And who said that we have to be experts the moment we arrive for orientation?