In the past year I have attended 3 restaurant weeks: Buckhead, Inman Park, and Midtown. For Buckhead Restaurant Week 2010 I tried Coast for the first time, and for Inman Park Restaurant Week 2010 I had my first visit (and only so far) at Rathbun's. This year I went to Ecco for Midtown Restaurant Week where I had been to once before. At least for Inman Park and Midtown Restaurant Weeks I carefully narrowed down the places I wanted to go to from several to 1 based on menus posted online and, naturally, reputation.
After arriving to Coast and Rathbun's for my reservations, it didn't take long to see the franticness that Restaurant Week probably added on top of their usual Friday and Saturday night business, at least I assume this is the case for Rathbun's. In general, the service wasn't great and the food was fine and probably in smaller portions. But when going somewhere like Rathbun's, I'm definitely not looking for "fine". I'm wanting great - and that shouldn't be compromised during Restaurant Week.
On the other hand, I went to Ecco on a Sunday night when the restaurant was maybe half full. This experience was much closer to a non-restaurant week experience with good service and great food.
When it comes down to it, $25 for a 3-course meal at a great restaurant will probably always be a draw to taste the town for many, but be prepared for an experience that may not be representative of what the restaurant offers on a regular basis.
To get your own taste of restaurant week, check out Inman Park Restaurant Week going on this week.