I use One Medical (http://www.onemedical.com). Yes, they have a membership fee, but it’s only $199/year. In my opinion, it’s well worth it. Every doctor I’ve encountered there has been very friendly and professional and, more importantly, competent. I always get same-day appointments, and when I show up, I’m seen exactly when my appointment is scheduled to begin. Their locations are also conveniently located next to major Metro stations. (In fact, I’m heading there today to get a flu shot–for free, no appointment necessary.) Sure, it’d be great to get this type of service without the membership fee, but in my experience, it doesn’t exist in DC. If you’re interested in giving them a shot (no pun intended), they give members coupon codes to give to friends. Here’s mine: REFDCQW812. It’s for 20% off the fee, and I think it’s good through the end of the month.