I eat out at least 4 nights a week, usually at upscale places...that said, I consider your experience anything but letterworthy; a letter will do nothing but make you look like a schlep. You could have maybe asked a manager on your way out why the delay was so long, but the bottom line is, your server compensated you for the problem. What else did you need at your table that the 3 visits prior to your food's arrival couldn't cover? It's a good possibility that you got a new waiter or maybe she forgot to put your order into the system right away. Either way, the manager will repremand her if the complementary objects were provided b/c of her mistakes. Generally upscale places allow a longer kitchen turnaround time as well; while an hour is still pretty long, she may be used to putting her orders in late to allow for appetizer or wine consumption. For future referrence, if you are going to write a letter, make sure it's intentions can in some way help the restaurant operate more effectively... if not, it just sounds like you are fishing for a free meal. That is TACKY.
PS. My old office is RIGHT next to bandera... I used to eat there a LOT ...the open-air grill area radiates great smells all day long, making it hard to resist come dinnertime. I've always had great service there and the waitresses used to all be super cute toO!